gbb_flags_common.sh: Add GBB_FLAG_ENABLE_UDC to help text

BUG=b:78577893
BRANCH=None
TEST=None

Change-Id: I1905f53aadb0ae882dc4cf9f4fd214b4ccdfc440
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1029429
Commit-Ready: Furquan Shaikh <furquan@chromium.org>
Tested-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Duncan Laurie <dlaurie@google.com>
diff --git a/scripts/image_signing/gbb_flags_common.sh b/scripts/image_signing/gbb_flags_common.sh
index 00b3485..5a9aee7 100644
--- a/scripts/image_signing/gbb_flags_common.sh
+++ b/scripts/image_signing/gbb_flags_common.sh
@@ -35,6 +35,7 @@
   GBB_FLAG_FORCE_DEV_BOOT_FASTBOOT_FULL_CAP  0x00002000
   GBB_FLAG_FORCE_MANUAL_RECOVERY             0x00004000
   GBB_FLAG_DISABLE_FWMP                      0x00008000
+  GBB_FLAG_ENABLE_UDC                        0x00010000
   "
 
 GBBFLAGS_DESCRIPTION_SUFFIX="