checkpatch: require commit text

Commit text is almost always necessary to explain why a change is
needed. Exceptions are rare enough that these can be granted through
manual checkpatch overrides.

Change-Id: I926b2276f717940c2fec77a6709fa3088b1bf0c3
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
(cherry picked from commit d3b3b64c907dbf2244250fc4b389562f2efedee2)