include/linux/kfifo.h: fix comment

include/linux/kfifo.h: fix comment

Clean up unusual formatting in the note about locking.

Link: http://lkml.kernel.org/r/20180324002630.13046-1-Valentin.Vidic@CARNet.hr
Signed-off-by: Valentin Vidic <Valentin.Vidic@CARNet.hr>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Sean Young <sean@mess.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>