[media] vb2: replace void *alloc_ctxs by struct device *alloc_devs

Make this a proper typed array. Drop the old allocate context code since
that is no longer used.

Note that the memops functions now get a struct device pointer instead of
the struct device ** that was there initially (actually a void pointer to
a struct containing only a struct device pointer).

This code is now a lot cleaner.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

samples/v4l/v4l2-pci-skeleton.c

@@ -163,7 +163,7 @@ static irqreturn_t skeleton_irq(int irq, void *dev_id)
  */
 static int queue_setup(struct vb2_queue *vq,
 		       unsigned int *nbuffers, unsigned int *nplanes,
-		       unsigned int sizes[], void *alloc_ctxs[])
+		       unsigned int sizes[], struct device *alloc_devs[])
 {
 	struct skeleton *skel = vb2_get_drv_priv(vq);