make_dev_ssd: Allow smaller kernel partition.

Some Brillo devices may have smaller kernel partition and we need to reduce the
size limit.

BUG=none
BRANCH=none
TEST=make_dev_ssd.sh applied on a Brillo config with 8MB kernel partition.

Change-Id: I9ca37445a6cdb20138f13dbe975c207383a1474c
Reviewed-on: https://chromium-review.googlesource.com/255341
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Mao Huang <littlecvr@chromium.org>
Commit-Queue: Hung-Te Lin <hungte@chromium.org>
1 file changed