V4L/DVB (9242): video: add sh_mobile_ceu comments

This patch adds CEU hardware block comments to the sh_mobile_ceu driver.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>