Asoc: msm: 8064: Set channel as Mono for Incall Music Delivery

For incall music delivery, there is only one share channel is
supported between MDM and APQ. If the media is stereo, afe tries to
open two share channels and causes music playback failure.
Add fixup fucntion to always set the channel as 1 whenever the media
is stereo or mono. And make sure only one share channel is opened.