[media] v4l2-ioctl.c: handle PREPARE_BUF like QUERYBUF

The core code for PREPARE_BUF didn't take the multiplanar case into account,
which might cause page faults. Handle PREPARE_BUF just like QUERYBUF and
QBUF/DQBUF.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -2188,6 +2188,7 @@ static int check_array_args(unsigned int cmd, void *parg, size_t *array_size,
 	int ret = 0;
 
 	switch (cmd) {
+	case VIDIOC_PREPARE_BUF:
 	case VIDIOC_QUERYBUF:
 	case VIDIOC_QBUF:
 	case VIDIOC_DQBUF: {