[media] v4l: omap4iss: Don't check for missing get_fmt op on remote subdev

The remote subdev of any video node in the OMAP4 ISS is an internal
subdev that is guaranteed to implement get_fmt. Don't check the return
value for -ENOIOCTLCMD, as this can't happen.

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>