build(psci): add build option for OS-initiated mode

Change-Id: Ie4f7b6a36926ab075ebb9c6507a3ff48ce5538fe
Signed-off-by: Wing Li <wingers@google.com>
diff --git a/Makefile b/Makefile
index b9ca664..46361f7 100644
--- a/Makefile
+++ b/Makefile
@@ -1114,6 +1114,7 @@
         PLAT_RSS_NOT_SUPPORTED \
         PROGRAMMABLE_RESET_ADDRESS \
         PSCI_EXTENDED_STATE_ID \
+        PSCI_OS_INIT_MODE \
         RESET_TO_BL31 \
         RESET_TO_BL31_WITH_PARAMS \
         SAVE_KEYS \
@@ -1256,6 +1257,7 @@
         PLAT_RSS_NOT_SUPPORTED \
         PROGRAMMABLE_RESET_ADDRESS \
         PSCI_EXTENDED_STATE_ID \
+        PSCI_OS_INIT_MODE \
         RAS_EXTENSION \
         RESET_TO_BL31 \
         RESET_TO_BL31_WITH_PARAMS \