CHROMIUM: PRESUBMIT.cfg: enforce s-o-b tags

Since repohooks is going to reject this by default, make sure the
kernel repos allow them.

BUG=None
TEST=`repo upload` works here

Change-Id: I3a68fa70b700f329e5760235bb26f41ae67a6635
Signed-off-by: Mike Frysinger <vapier@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1897963