checkpatch: add --types option to report only specific message types

Add a --types convenience option to show only specific message types.
Combined with the --fix option, this can produce specific suggested
formatting patches to files.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>