media: uvcvideo: Do not return positive errors in uvc_query_ctrl()

If the returned size of the query does not match the expected size or it
is zero, return -EPIPE instead of 0 or a positive value.

This will avoid confusing the caller (and ultimately userspace) that
doesn't expect a positive or zero value.
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

drivers/media/usb/uvc/uvc_video.c

@@ -83,7 +83,7 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
 		dev_err(&dev->udev->dev,
 			"Failed to query (%s) UVC control %u on unit %u: %d (exp. %u).\n",
 			uvc_query_name(query), cs, unit, ret, size);
-		return ret;
+		return ret < 0 ? ret : -EPIPE;
 	}
 
 	/* Reuse data[0] to request the error code. */