[media] saa7134: remove dev from saa7134_fh, use saa7134_fh for empress node

Use the saa7134_fh struct for the empress video node as well, drop the dev
pointer from that struct since we can use drvdata for that.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>