V4L/DVB (7918): au0828: remove irrelevent analog tuner standby code

This code is irrelevant to this driver and should be removed.  This was
copied from a hack in cx88-dvb.c, which prevents noise coming from the
analog tuner (via an audio patch cable from the pci card to the sound
hardware) when in digital mode by muting the tda988x.  This issue does
not apply to this USB hybrid chip design, where a single piece of
silicon handles both analog and digital demodulation.

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