[media] m88rs2000: LNB voltage control implemented

Trival patch to get it working with my cards stuff.

Signed-off-by: Igor M. Liplianin <liplianin@me.by>
Acked-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>