[media] media: omap3isp: video: Don't call vb2 mmap with queue lock held

videobuf2 has long been subject to AB-BA style deadlocks due to the
queue lock and mmap_sem being taken in different orders for the mmap
operation. The problem has been fixed by making this operation callable
without taking the queue lock, using an mmap_lock internal to videobuf2.

The omap3isp driver still calls the mmap operation with the queue lock
held, resulting in a potential deadlock. As the operation can now be
called without locking the queue, fix it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>