[media] omap3: Add function to register omap3isp platform device structure

The omap3isp platform device requires platform data. Instead of
registering the device in omap2_init_devices(), export an
omap3_init_camera() function to fill the device structure with the
platform data pointer and register the device.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>