[media] lmedm04: PID filtering changes

Improve PID filtering and program register 20 correctly.
 Make sure stream_on message is sent if streaming is off, otherwise
 PIDs are not registered.
 Move mutex outside lme2510_enable_pid.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>