More non-ATH_DEBUG build fixes.
Update snd quirks for T520, T420, X220.

Group onboard mic and headphone mic jack together.  Creates association that
will switch between microphone inputs depending on the state of the headphone
jack being connected to a live mic.

Fixes onboard mic not working at all on T520.

Tested on T520, T420.
Suspect X220 needs this too, untested on.

MFC after:	1 month