V4L/DVB (12504): soc-camera: prepare soc_camera_platform.c and its users for conversion

soc_camera_platform.c is only used by y SuperH ap325rxa board. This patch
converts soc_camera_platform.c and its users for the soc-camera platform-
device conversion and also extends soc-camera core to handle non-I2C cameras.

Cc: Paul Mundt <lethal@linux-sh.org>
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>