media: rcar-vin: Add support for outputting NV12

Most Gen3 boards can output frames in NV12 format, add support for this
with a runtime check that the running hardware supports it.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>