[media] mxl111sf-tuner: tune SYS_ATSCMH just like SYS_ATSC

The MxL111SF tuner is programmed the same way for ATSC-MH
as it is programmed for ATSC.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>