V4L/DVB (6230): dvb-pll: add module option to force dvb-pll desc id (for debug use only)

Add a module option to force the dvb-pll module to use an alternate dvb-pll
description without having to recompile the kernel.

Having a module option like this is useful in some cases, where the vendor
may release an alternate revision of the hardware using a different tuner,
but without changing the pci subsystem / usb device ids.

This option is intended for debugging purposes _only_.

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