A V4L2 standards mask may contain several standards. A more restricted
mask with just one standard is used when user needs to bind to an specific
standard that can't be auto-detect among a more generic mask.

So, Improve the autodetection logic to detect the correct audio standard
most of the time.

Based on a patch made by Dmitri Belimov <d.belimov@gmail.com>.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>