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_common.mk b/plat/arm/common/arm_common.mk
index 425e0d3..973e583 100644
--- a/plat/arm/common/arm_common.mk
+++ b/plat/arm/common/arm_common.mk
@@ -77,6 +77,11 @@
 $(eval $(call assert_boolean,ARM_CONFIG_CNTACR))
 $(eval $(call add_define,ARM_CONFIG_CNTACR))
 
+# Process ARM_BL31_IN_DRAM flag
+ARM_BL31_IN_DRAM		:=	0
+$(eval $(call assert_boolean,ARM_BL31_IN_DRAM))
+$(eval $(call add_define,ARM_BL31_IN_DRAM))
+
 PLAT_INCLUDES		+=	-Iinclude/common/tbbr				\
 				-Iinclude/plat/arm/common			\
 				-Iinclude/plat/arm/common/aarch64