Prevent RAS register access from lower ELs

This patch adds a build config 'RAS_TRAP_LOWER_EL_ERR_ACCESS' to set
SCR_EL3.TERR during CPU boot. This bit enables trapping RAS register
accesses from EL1 or EL2 to EL3.

RAS_TRAP_LOWER_EL_ERR_ACCESS is disabled by default.

Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
Change-Id: Ifb0fb0afedea7dd2a29a0b0491a1161ecd241438
diff --git a/Makefile b/Makefile
index a0d2ae0..bc5604b 100644
--- a/Makefile
+++ b/Makefile
@@ -900,6 +900,7 @@
 $(eval $(call assert_boolean,ENCRYPT_BL31))
 $(eval $(call assert_boolean,ENCRYPT_BL32))
 $(eval $(call assert_boolean,ERRATA_SPECULATIVE_AT))
+$(eval $(call assert_boolean,RAS_TRAP_LOWER_EL_ERR_ACCESS))
 
 $(eval $(call assert_numeric,ARM_ARCH_MAJOR))
 $(eval $(call assert_numeric,ARM_ARCH_MINOR))
@@ -979,6 +980,7 @@
 $(eval $(call add_define,BL2_INV_DCACHE))
 $(eval $(call add_define,USE_SPINLOCK_CAS))
 $(eval $(call add_define,ERRATA_SPECULATIVE_AT))
+$(eval $(call add_define,RAS_TRAP_LOWER_EL_ERR_ACCESS))
 
 ifeq (${SANITIZE_UB},trap)
         $(eval $(call add_define,MONITOR_TRAPS))