pal: add new mutex to synchronize getParam mixer ctl call to AGM

Earlier getParam call to AGM was synchronized with resourceManager
mutex. This was causing delay for get parameters in Resource Manager,
as it will be waiting for resourceManager mutex lock.

In cases where there was a concurrency of low latency and offloaded
stream on BT, get encoder latency param for ll stream was getting
blocked due to resourceManager mutex previously acquired by getTimestamp
call for offloaded stream. This was leading to delay in write calls for
ll stream, and thus causing glitches over BT.

Fixed this by introducing mGetParamMutex, which will be used to sync
getParam mixer control calls to AGM.

Change-Id: Ib8ea246c1836f6d4d96912f13c939da003dae8d9
2 files changed