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>
diff --git a/src/vboot/callbacks/headless_stub.c b/src/vboot/callbacks/headless_stub.c
index 1edf8f4..5a9ae40 100644
--- a/src/vboot/callbacks/headless_stub.c
+++ b/src/vboot/callbacks/headless_stub.c
@@ -37,6 +37,13 @@
 	return display_screen((enum VbScreenType_t)screen_type);
 }
 
+VbError_t VbExDisplayMenu(uint32_t screen_type, uint32_t locale,
+			  uint32_t selected_index, uint32_t redraw_base)
+{
+	printf("%s:%d invoked\n", __func__, __LINE__);
+	return VBERROR_SUCCESS;
+}
+
 VbError_t VbExDisplayImage(uint32_t x, uint32_t y,
 			   void *buffer, uint32_t buffersize)
 {