[media] uvcvideo: Fix ENUMINPUT handling

Properly validate the user-supplied index against the number of inputs.
The code used the pin local variable instead of the index by mistake.

Reported-by: Jozef Vesely <vesely@gjh.sk>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/uvc/uvc_v4l2.c

@@ -694,7 +694,7 @@ static long uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 					break;
 			}
 			pin = iterm->id;
-		} else if (pin < selector->bNrInPins) {
+		} else if (index < selector->bNrInPins) {
 			pin = selector->baSourceID[index];
 			list_for_each_entry(iterm, &chain->entities, chain) {
 				if (!UVC_ENTITY_IS_ITERM(iterm))