Introduce `el3_runtime` and `PSCI` libraries

This patch moves the PSCI services and BL31 frameworks like context
management and per-cpu data into new library components `PSCI` and
`el3_runtime` respectively. This enables PSCI to be built independently from
BL31. A new `psci_lib.mk` makefile is introduced which adds the relevant
PSCI library sources and gets included by `bl31.mk`. Other changes which
are done as part of this patch are:

* The runtime services framework is now moved to the `common/` folder to
  enable reuse.
* The `asm_macros.S` and `assert_macros.S` helpers are moved to architecture
  specific folder.
* The `plat_psci_common.c` is moved from the `plat/common/aarch64/` folder
  to `plat/common` folder. The original file location now has a stub which
  just includes the file from new location to maintain platform compatibility.

Most of the changes wouldn't affect platform builds as they just involve
changes to the generic bl1.mk and bl31.mk makefiles.

NOTE: THE `plat_psci_common.c` FILE HAS MOVED LOCATION AND THE STUB FILE AT
THE ORIGINAL LOCATION IS NOW DEPRECATED. PLATFORMS SHOULD MODIFY THEIR
MAKEFILES TO INCLUDE THE FILE FROM THE NEW LOCATION.

Change-Id: I6bd87d5b59424995c6a65ef8076d4fda91ad5e86
diff --git a/lib/psci/aarch64/psci_entry.S b/lib/psci/aarch64/psci_entry.S
new file mode 100644
index 0000000..646ebcf
--- /dev/null
+++ b/lib/psci/aarch64/psci_entry.S
@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <arch.h>
+#include <asm_macros.S>
+#include <el3_common_macros.S>
+#include <psci.h>
+#include <xlat_tables.h>
+
+	.globl	psci_entrypoint
+	.globl	psci_power_down_wfi
+
+	/* --------------------------------------------------------------------
+	 * This CPU has been physically powered up. It is either resuming from
+	 * suspend or has simply been turned on. In both cases, call the power
+	 * on finisher.
+	 * --------------------------------------------------------------------
+	 */
+func psci_entrypoint
+	/*
+	 * On the warm boot path, most of the EL3 initialisations performed by
+	 * 'el3_entrypoint_common' must be skipped:
+	 *
+	 *  - Only when the platform bypasses the BL1/BL31 entrypoint by
+	 *    programming the reset address do we need to set the CPU endianness.
+	 *    In other cases, we assume this has been taken care by the
+	 *    entrypoint code.
+	 *
+	 *  - No need to determine the type of boot, we know it is a warm boot.
+	 *
+	 *  - Do not try to distinguish between primary and secondary CPUs, this
+	 *    notion only exists for a cold boot.
+	 *
+	 *  - No need to initialise the memory or the C runtime environment,
+	 *    it has been done once and for all on the cold boot path.
+	 */
+	el3_entrypoint_common					\
+		_set_endian=PROGRAMMABLE_RESET_ADDRESS		\
+		_warm_boot_mailbox=0				\
+		_secondary_cold_boot=0				\
+		_init_memory=0					\
+		_init_c_runtime=0				\
+		_exception_vectors=runtime_exceptions
+
+	/* --------------------------------------------
+	 * Enable the MMU with the DCache disabled. It
+	 * is safe to use stacks allocated in normal
+	 * memory as a result. All memory accesses are
+	 * marked nGnRnE when the MMU is disabled. So
+	 * all the stack writes will make it to memory.
+	 * All memory accesses are marked Non-cacheable
+	 * when the MMU is enabled but D$ is disabled.
+	 * So used stack memory is guaranteed to be
+	 * visible immediately after the MMU is enabled
+	 * Enabling the DCache at the same time as the
+	 * MMU can lead to speculatively fetched and
+	 * possibly stale stack memory being read from
+	 * other caches. This can lead to coherency
+	 * issues.
+	 * --------------------------------------------
+	 */
+	mov	x0, #DISABLE_DCACHE
+	bl	bl31_plat_enable_mmu
+
+	bl	psci_power_up_finish
+
+	b	el3_exit
+endfunc psci_entrypoint
+
+	/* --------------------------------------------
+	 * This function is called to indicate to the
+	 * power controller that it is safe to power
+	 * down this cpu. It should not exit the wfi
+	 * and will be released from reset upon power
+	 * up. 'wfi_spill' is used to catch erroneous
+	 * exits from wfi.
+	 * --------------------------------------------
+	 */
+func psci_power_down_wfi
+	dsb	sy		// ensure write buffer empty
+	wfi
+	bl	plat_panic_handler
+endfunc psci_power_down_wfi
+