[media] saa7134: share resource management between normal and empress nodes

The empress video node can share resource management with the normal
video nodes, thus allowing for code sharing and making the empress node
non-exclusive.

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