CHROMIUM: md: dm-verity-chromeos: changed how kernel parititon is corrupted

CHROMIUM: md: dm-verity-chromeos: changed how kernel parititon is corrupted

Changed the error handling to use the linux cmdline
to find the kernel partition to corrupt it so when
an error is detected in the root volume, the bios
will know to switch partitions.

BUG=chromium:222954
TEST=1. manually corrupt root partition and bootcache and reboot 2. manually corrupted root paritions with no bootcache
Signed-off-by: Paul Taysom <taysom@chromium.org>
Change-Id: I9ea8c5462d573fc8599be36b4c6eaf1f4c7eb99c
Reviewed-on: https://gerrit.chromium.org/gerrit/46375
Tested-by: Paul Taysom <taysom@chromium.org>
Reviewed-by: Will Drewry <wad@chromium.org>
Commit-Queue: Paul Taysom <taysom@chromium.org>