ASoC: msm: fix lowlatency playback and FM concurrency issue

Lowlatency playback is failed to start when FM is going on because
of wrong channel count in backend DAI. Channels are overwritten because
of afe loopback port mixer caching variable(port_sessions) overflow.
Fix this issue by creating an array to track all the loopback
connections.

Change-Id: I47b875df7eae671f8b59ecc76f61ed7fc7147f0e
Signed-off-by: Vidyakumar Athota <vathota@codeaurora.org>