feat(fvp): add stub function to retrieve DLME image auth features

DLME image authentication features are currently not supported on FVP.
This patch introduces a stub function in fvp_drtm_stub.c as a
placeholder for retrieving DLME image authentication features.

Change-Id: I6d274834245774c5442d67ee93fcd641f3a9cd1a
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/plat/arm/board/fvp/fvp_drtm_stub.c b/plat/arm/board/fvp/fvp_drtm_stub.c
index 213a7e3..238febd 100644
--- a/plat/arm/board/fvp/fvp_drtm_stub.c
+++ b/plat/arm/board/fvp/fvp_drtm_stub.c
@@ -38,3 +38,8 @@
 {
 	return 0ULL;
 }
+
+uint64_t plat_drtm_get_dlme_img_auth_features(void)
+{
+	return 0ULL;
+}