mod_image_for_recovery.sh: Update kern_b_hash from SHA1 to SHA256

We're changing the algorithm for this so the build scripts need to be
adapted in sync.

BUG=b:137576540
TEST=Built recovery image and ran it on Kevin.

Cq-Depend: chromium:1707529
Change-Id: Idbfa33ff21ca1e947acaf748f4a45642291133fd
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1707510
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed