vboot: add debug message for VB_SCREEN_OS_BROKEN

This change adds a fallback text for VB_SCREEN_OS_BROKEN, which is shown
when the screen is not supported.

BUG=chromium:501060
BRANCH=master
TEST=Tested on Samus
CQ-DEPEND=CL:304404

Change-Id: I0f35ec873532fcfe6782ccff89d54798152f7fb3
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/305252
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
1 file changed