vboot: Publicize check_reboot_for_display()

Publicize check_reboot_for_display() and rename it to
vb2api_need_reboot_for_display() for depthcharge to use.

BRANCH=none
BUG=chromium:1030608
TEST=FEATURES=test emerge-nami vboot_reference

Change-Id: Ie6c734850b67b29c8a098c3f232888f3ab47fddf
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1957726
Reviewed-by: Joel Kitching <kitching@chromium.org>
5 files changed