SPMD: save/restore EL2 system registers.

NOTE: Not all EL-2 system registers are saved/restored.
This subset includes registers recognized by ARMv8.0

Change-Id: I9993c7d78d8f5f8e72d1c6c8d6fd871283aa3ce0
Signed-off-by: Jose Marinho <jose.marinho@arm.com>
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Signed-off-by: Artsem Artsemenka <artsem.artsemenka@arm.com>
Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index 60958a1..8e1f273 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -262,3 +262,8 @@
 
 # Enable Link Time Optimization
 ENABLE_LTO			:= 0
+
+# Build flag to include EL2 registers in cpu context save and restore during
+# S-EL2 firmware entry/exit. This flag is to be used with SPD=spmd option.
+# Default is 0.
+CTX_INCLUDE_EL2_REGS		:= 0