[media] vpif_display: fix cleanup code

The cleanup sequence was incorrect and could cause a kernel oops.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Tested-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>