We always probe the Pro Audio profile with the maximum number of
channels but this can lead to a more limited amount of sample rates.
Add an option to set the channels used when probing so that the other
samplerates become available.
Fixes#2990
libacp is a port and wrapper around the pulseaudio card profile code.
It uses a set of templates for construct a card profile and mixer port
settings. It also has support for UCM when available for the hardware.
