V4L/DVB (10084): sh_mobile_ceu: add NV12 and NV21 support

This patch adds NV12/NV21 support 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>