vboot: Add a blinking cursor to the vendor prompt

Add support to show a blinking cursor after the vendor data entry
so that users can tell that an entry is required.

BUG=b:138812835
TEST=Test on a Drallion device with an updated Depthcharge
BRANCH=drallion

Cq-Depend: chromium:2120311
Change-Id: I02073d92d02a4171f337f86f880d660eb5d8b6f1
Signed-off-by: Mathew King <mathewk@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2120310
Reviewed-by: Pranay Shoroff <pshoroff@google.com>
3 files changed