V4L/DVB (8338): soc_camera: Move spinlocks

This patch moves the spinlock handling from soc_camera.c to the actual
camera host driver. The spinlock_alloc/free callbacks are replaced with
code in init_videobuf(). So far all camera host drivers implement their
own spinlock_alloc/free methods anyway, and videobuf_queue_core_init()
BUGs on a NULL spinlock argument, so, new camera host drivers will not
forget to provide a spinlock when initialising their videobuf queues.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>