V4L/DVB (10278): cx18: Fix bad audio in first analog capture.

Normalize the APU state before the second firmware load so that audio
for the first analog capture is correct.

Many thanks to Conexant for supporting me in finding a solution for this
problem.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>