[media] af9013: fix AF9013 TDA18271 IF config

IF freq	for DVB-T 7 MHz	and 8 MHz was set slightly wrong. Due to that it
didn't worked at all (?) for 7 MHz channels and most likely performance
was dropped for 8 MHz channels.

That bug was pointed by few people during last two months. Thank you.

Trivial fix. Compile tested only due to lack of proper HW and signal.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Cc: Romolo Manfredini <romoloman@hotmail.com>
Cc: Alireza Moini <alireza.moini@silverbrookresearch.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>