checkpatch: quiet Kconfig help message checking

Editing Kconfig dependencies can emit unnecessary messages about missing
or too short help entries.

Only emit the message when adding help sections to Kconfig files.

Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Jean Delvare <jdelvare@suse.de>
Tested-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>