[media] soc_camera: Add RGB666 & RGB888 formats

Based on work done by Katsuya Matsubara.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>