ASoC: msm: Add AIO support for multi channel pcm platform driver

Add Async write mechanism for multichannel PCM platform driver.
This will facilitate to have meta data information flow from apps
To DSP and vice versa.

Change-Id: I0c7238b997588fd5ef9946a7dc83bfbe9ce1a1f7
Signed-off-by: Santosh Mardi <gsantosh@codeaurora.org>