Add support to load BL31 in DRAM

This patch adds an option to the ARM common platforms to load BL31 in the
TZC secured DRAM instead of the default secure SRAM.

To enable this feature, set `ARM_BL31_IN_DRAM` to 1 in build options.
If TSP is present, then setting this option also sets the TSP location
to DRAM and ignores the `ARM_TSP_RAM_LOCATION` build flag.

To use this feature, BL2 platform code must map in the DRAM used by
BL31. The macro ARM_MAP_BL31_SEC_DRAM is provided for this purpose.
Currently, only the FVP BL2 platform code maps in this DRAM.

Change-Id: If5f7cc9deb569cfe68353a174d4caa48acd78d67
diff --git a/plat/arm/common/arm_bl2_setup.c b/plat/arm/common/arm_bl2_setup.c
index 97c2bca..a528830 100644
--- a/plat/arm/common/arm_bl2_setup.c
+++ b/plat/arm/common/arm_bl2_setup.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2016, 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:
@@ -96,11 +96,27 @@
 #pragma weak bl2_plat_get_bl33_meminfo
 #pragma weak bl2_plat_set_bl33_ep_info
 
+#if ARM_BL31_IN_DRAM
+meminfo_t *bl2_plat_sec_mem_layout(void)
+{
+	static meminfo_t bl2_dram_layout
+		__aligned(CACHE_WRITEBACK_GRANULE) = {
+		.total_base = BL31_BASE,
+		.total_size = (ARM_AP_TZC_DRAM1_BASE +
+				ARM_AP_TZC_DRAM1_SIZE) - BL31_BASE,
+		.free_base = BL31_BASE,
+		.free_size = (ARM_AP_TZC_DRAM1_BASE +
+				ARM_AP_TZC_DRAM1_SIZE) - BL31_BASE
+	};
 
+	return &bl2_dram_layout;
+}
+#else
 meminfo_t *bl2_plat_sec_mem_layout(void)
 {
 	return &bl2_tzram_layout;
 }
+#endif
 
 /*******************************************************************************
  * This function assigns a pointer to the memory that the platform has kept