ASoC: msm: add proxy port and pcm backend in machine driver

* Add additional proxy port frontend and pcm backend to support dual proxy port
* Add channel configuration mixer control for second proxy port

Change-Id: Iba7e21f17122926d27acc58be653351b4d0ea37a
Signed-off-by: Alexy Joseph <alexyj@codeaurora.org>
Signed-off-by: Tahir Dawson <dawson@codeaurora.org>