[media] ov2640: fix colorspace handling

The colorspace is independent of whether YUV or RGB is sent to the SoC.
Fix this.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>