feat(bl2): add support to separate no-loadable sections

Add new options SEPARATE_BL2_NOLOAD_REGION to separate no-loadable
sections (.bss, stack, page tables) to a ram region specified
by BL2_NOLOAD_START and BL2_NOLOAD_LIMIT.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>
Change-Id: I844ee0fc405474af0aff978d292c826fbe0a82fd
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index b39dcf4..910ffdf 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -250,6 +250,10 @@
 # separate memory region, which may be discontiguous from the rest of BL31.
 SEPARATE_NOBITS_REGION		:= 0
 
+# Put BL2 NOLOAD sections (.bss, stacks, page tables) in a separate memory
+# region, platform Makefile is free to override this value.
+SEPARATE_BL2_NOLOAD_REGION	:= 0
+
 # If the BL31 image initialisation code is recalimed after use for the secondary
 # cores stack
 RECLAIM_INIT_CODE		:= 0