[media] v4l2-ioctl: allow all controls if ctrl_class == 0

The check_ext_ctrls() function in v4l2-ioctl.c checks if all controls in the
control array are from the same control class as c->ctrl_class. However,
that check should only be done if c->ctrl_class != 0. A 0 value means
that this restriction does not apply.

So return 1 (OK) if c->ctrl_class == 0.

Found by running v4l2-compliance on the uvc driver.

Signed-off-by: Hans Verkuil <[e-mail]>
Acked-by: Sakari Ailus <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

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

···
 	 */
 	if (!allow_priv && c->ctrl_class == V4L2_CID_PRIVATE_BASE)
 		return 0;
+	if (c->ctrl_class == 0)
+		return 1;
 	/* Check that all controls are from the same control class. */
 	for (i = 0; i < c->count; i++) {
 		if (V4L2_CTRL_ID2CLASS(c->controls[i].id) != c->ctrl_class) {