[media] m88rs2000: make use ts2020

Tuner part of Montage rs2000 chip is similar to ts2020 tuner.
Patch to use ts2020 code.

[mchehab@redhat.com: a few CodingStyle fixes]
Signed-off-by: Igor M. Liplianin <liplianin@me.by>

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>