lib: el3_runtime: Conditionally save/restore EL2 NEVE registers

Include EL2 registers related to Nested Virtualization in EL2 context
save/restore routines if architecture supports it and platform wants to
use these features in Secure world.

Change-Id: If006ab83bbc2576488686f5ffdff88b91adced5c
Signed-off-by: Arunachalam Ganapathy <arunachalam.ganapathy@arm.com>
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index bc4982d..578bd59 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -62,6 +62,11 @@
 # world. It is not needed to use it in the Non-secure world.
 CTX_INCLUDE_PAUTH_REGS		:= 0
 
+# Include Nested virtualization control (Armv8.4-NV) registers in cpu context.
+# This must be set to 1 if architecture implements Nested Virtualization
+# Extension and platform wants to use this feature in the Secure world
+CTX_INCLUDE_NEVE_REGS		:= 0
+
 # Debug build
 DEBUG				:= 0