2lib: Add recovery reason VB2_RECOVERY_WIDEVINE_PREPARE

BUG=b:248610274
TEST=CQ
BRANCH=none

Change-Id: I4b4487cc4cab77bbe9cfe323ee00d649c55c30f6
Signed-off-by: Yi Chou <yich@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/4885870
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>
2 files changed