V4L/DVB (8600): au0828: explicitly set 6 MHz IF frequency in hauppauge_hvr950q_config

Explicitly set 6 MHz IF frequency for VSB and QAM in
hauppauge_hvr950q_config.

The default value is 6 MHz, so this patch doesn't change anything --
this only improves code readability and may prevent future bugs.

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