[media] uvcvideo: Cleanup leftovers of partial revert

Commit ba68c8530a263dc4de440fa10bb20a1c5b9d4ff5 (Partly revert "[media]
uvcvideo: Set error_idx properly for extended controls API failures")
missed two modifications. Clean them up.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>