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>