presubmit: enable checkpatch

So that I can stop nit-picking on basic whitespace things in CLs.

BUG=none
TEST=run presubmit

Change-Id: I9077b78db9a33596cbefbca44a78c95bd4edc54a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/mosys/+/2302953
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>
Commit-Queue: Paul Fagerburg <pfagerburg@chromium.org>