[media] v4l: soc-camera: Store negotiated buffer settings

This fixes the problem in which a host driver
sets a personalized sizeimage or bytesperline field,
and gets ignored when doing G_FMT.

Signed-off-by: Sergio Aguirre <saaguirre@ti.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>