V4L/DVB (7390): saa7134: clear audio DSP interface after access error

In the case of an access error to the high latency registers of
the audio DSP, the interface needs to be cleared, otherwise a cascade
of errors occurs.

This patch is closely modeled after a proposal by Mirek Slugen

Signed-off-by: Hartmut Hackmann <hartmut.hackmann@t-online.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>