[media] drx-j: be sure to use tuner's IF

Instead of just hardcoding an IF value of 5MHz, use the one
provided by the tuner, with can be different for QAM and
VSB.

Acked-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>