[media] mn88473: implement lock for all delivery systems

Add capability to check if digital TV has lock for all delivery
systems.

Signed-off-by: Benjamin Larsson <benjamin@southpole.se>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>