feat(sys_reg_trace): enable trace system registers access from lower NS ELs

Introduced a build flag 'ENABLE_SYS_REG_TRACE_FOR_NS' to enable trace
system registers access in NS-EL2, or NS-EL1 (when NS-EL2 is
implemented but unused).

Change-Id: Idc1acede4186e101758cbf7bed5af7b634d7d18d
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/Makefile b/Makefile
index c8ffdab..5de0e07 100644
--- a/Makefile
+++ b/Makefile
@@ -965,6 +965,7 @@
         ENABLE_FEAT_SB \
         PSA_FWU_SUPPORT \
         ENABLE_TRBE_FOR_NS \
+        ENABLE_SYS_REG_TRACE_FOR_NS \
 )))
 
 $(eval $(call assert_numerics,\
@@ -1066,6 +1067,7 @@
         NR_OF_IMAGES_IN_FW_BANK \
         PSA_FWU_SUPPORT \
         ENABLE_TRBE_FOR_NS \
+        ENABLE_SYS_REG_TRACE_FOR_NS \
 )))
 
 ifeq (${SANITIZE_UB},trap)