ASoC: msm: Add LAB support in platform driver

LAB feature is used in listen for capturing PCM
data on successfull keyword detection from codec.
This change adds support for reading PCM through
pcm ops and controling LAB feature to enable, disable
and to stop LAB after capturing required amount of
PCM data.

Change-Id: I39d3f9e98442f0880fc33d8f7a7144134311db09
Signed-off-by: Venkat Sudhir <vsudhir@codeaurora.org>
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>