V4L/DVB (8607): cxusb: fix OOPS and broken tuning regression on FusionHDTV Dual Digital 4

quoting Robert Lowery:

I think I've found the cause of the oops.
[...]
BTW it appears I have fixed my tuning problems with the updated patch
below.  This reverts a change Mauro made a while back.

All is good now  :)
[...]
The good news is that I've got a better patch that definitely works this
time and even better, makes use of the standard firmware (rather than
the Australian specific one).

...based on an earlier patch by Hans-Frieder Vogt:
http://www.linuxtv.org/pipermail/linux-dvb/2008-May/026280.html

Signed-off-by: Robert Lowery <rlowery@exemail.com.au>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>