fix(amu): add default value for ENABLE_FEAT_FGT and ENABLE_FEAT_ECV flags

ENABLE_FEAT_FGT and ENABLE_FEAT_ECV macros are used to access
HDFGRTR_EL2 and CNTPOFF_EL2 registers respectively. These flags are set
to true for v8.6 and upwards and are not handled explicitly for lower
architecture versions.

This patch adds definitive default value to these build macros, so that
for v8.5 and below, they are not overridden and set to true by the gcc.

Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
Change-Id: Ic300194c8ad77558be9a0e00153e42185bf2c58c
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index 595ba7b..72f5e33 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -139,6 +139,12 @@
 # Flag to enable access to the HAFGRTR_EL2 register
 ENABLE_FEAT_AMUv1		:= 0
 
+# Flag to enable access to the HDFGRTR_EL2 register
+ENABLE_FEAT_FGT			:= 0
+
+# Flag to enable access to the CNTPOFF_EL2 register
+ENABLE_FEAT_ECV			:= 0
+
 # By default BL31 encryption disabled
 ENCRYPT_BL31			:= 0