V4L/DVB (9918): cx88: advise/acquire clean-up for HVR-1300/3000/4000

This cleans-up the advise/acquire methods.

This has been tested on the hvr-1300/4000 and assumed to be
correct on the hvr-3000.

This update also fixes analogue tuning on the hvr-1300
when in blackbird mode.

Signed-off-by: Darron Broad <darron@kewl.org>
Cc: Steven Toth <stoth@hauppauge.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>