detachables: Add VbExDisplayMenu def to headless_stub

Left out definition of VbExDisplayMenu for devices
that don't use the display driver.

BUG=b:35585623
BRANCH=None
TEST=./build_packages --board=gale

Change-Id: Iabd56f26f5d1441f8a45b454b578fa54a4be5128
Signed-off-by: Shelley Chen <shchen@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/517310
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
1 file changed