checkpatch: fix typo in comment

Link: http://lkml.kernel.org/r/20170902175249.15bb77f2@endymion


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