app: aboot: zero out extra bits, while update misc partition.

Zeored out extra bits while updating misc parition.

Issue: SEC-2021
Change-Id: I9f57a78b00360b7ee464cd0c76540de8d9784555
(cherry picked from commit 0d06ad00c8d6630cd90016226c7d68eedb5a1132)
1 file changed