V4L/DVB (12505): soc_camera_platform: pass device pointer from soc-camera core on .add_device()

Add a struct device pointer to struct soc_camera_platform_info and let the user
(ap325rxa) pass it down to soc_camera_platform.c in its .add_device() method.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>