BL31: Enable pointer authentication support

The size increase after enabling options related to ARMv8.3-PAuth is:

+----------------------------+-------+-------+-------+--------+
|                            |  text |  bss  |  data | rodata |
+----------------------------+-------+-------+-------+--------+
| CTX_INCLUDE_PAUTH_REGS = 1 |  +192 | +1536 |   +0  |   +0   |
|                            |  0.3% |  3.1% |       |        |
+----------------------------+-------+-------+-------+--------+
| ENABLE_PAUTH = 1           | +1848 | +1536 |  +16  |   +0   |
|                            |  3.3% |  3.1% |  3.1% |        |
+----------------------------+-------+-------+-------+--------+

Results calculated with the following build configuration:

    make PLAT=fvp SPD=tspd DEBUG=1 \
    SDEI_SUPPORT=1                 \
    EL3_EXCEPTION_HANDLING=1       \
    TSP_NS_INTR_ASYNC_PREEMPT=1    \
    CTX_INCLUDE_PAUTH_REGS=1       \
    ENABLE_PAUTH=1

Change-Id: I43db7e509a4f39da6599ec2faa690d197573ec1b
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/bl31/bl31_main.c b/bl31/bl31_main.c
index da35f75..aca16d6 100644
--- a/bl31/bl31_main.c
+++ b/bl31/bl31_main.c
@@ -64,6 +64,27 @@
 }
 
 /*******************************************************************************
+ * Setup function for BL31.
+ ******************************************************************************/
+void bl31_setup(u_register_t arg0, u_register_t arg1, u_register_t arg2,
+		u_register_t arg3)
+{
+	/* Perform early platform-specific setup */
+	bl31_early_platform_setup2(arg0, arg1, arg2, arg3);
+
+	/*
+	 * Update pointer authentication key before the MMU is enabled. It is
+	 * saved in the rodata section, that can be writen before enabling the
+	 * MMU. This function must be called after the console is initialized
+	 * in the early platform setup.
+	 */
+	bl_handle_pauth();
+
+	/* Perform late platform-specific setup */
+	bl31_plat_arch_setup();
+}
+
+/*******************************************************************************
  * BL31 is responsible for setting up the runtime services for the primary cpu
  * before passing control to the bootloader or an Operating System. This
  * function calls runtime_svc_init() which initializes all registered runtime