feat(sctlr2): add support for FEAT_SCTLR2

Arm v8.9 introduces FEAT_SCTLR2, adding SCTLR2_ELx registers.
Support this, context switching the registers and disabling
traps so lower ELs can access the new registers.

Change the FVP platform to default to handling this as a dynamic option
so the right decision can be made by the code at runtime.

Change-Id: I0c4cba86917b6b065a7e8dd6af7daf64ee18dcda
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
diff --git a/make_helpers/arch_features.mk b/make_helpers/arch_features.mk
index 9cd5011..9533e98 100644
--- a/make_helpers/arch_features.mk
+++ b/make_helpers/arch_features.mk
@@ -90,7 +90,7 @@
 
 # Enable the features which are mandatory from ARCH version 8.9 and upwards.
 ifeq "8.9" "$(word 1, $(sort 8.9 $(ARM_ARCH_MAJOR).$(ARM_ARCH_MINOR)))"
-armv8-9-a-feats         := ENABLE_FEAT_TCR2 ENABLE_FEAT_DEBUGV8P9
+armv8-9-a-feats         := ENABLE_FEAT_TCR2 ENABLE_FEAT_DEBUGV8P9 ENABLE_FEAT_SCTLR2
 # 8.8 Compliant
 armv8-9-a-feats         += ${armv8-8-a-feats}
 FEAT_LIST               := ${armv8-9-a-feats}
@@ -219,6 +219,9 @@
 # Flag to enable access to TCR2 (FEAT_TCR2).
 ENABLE_FEAT_TCR2		?=	0
 
+# Flag to enable access to SCTLR2 (FEAT_SCTLR2).
+ENABLE_FEAT_SCTLR2		?=	0
+
 #
 ################################################################################
 # Optional Features defaulted to 0 or 2, if they are not enabled from