[media] it913x: support for different tuner regs

There appears to be differences in the tuner registers
on earlier IT9135 devices.

Using the current IT9137 settings cause corruptions on
some channels

This patch is in preparation for multi firmware loading and
current unsupported types.

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