LoudnessEnhancer : Improve the libeffects implementation

Context uses sampling rate from mCommon param now.
Added log tag for LoudnessEnhancerContext.
Added status check before processing the audio effect.
Initialise mGain varaible.
Guard mState by mutex.

Bug: 258124419
Test: atest VtsHalLoudnessEnhancerTargetTest
Change-Id: If1e5b47603c65e449147005b525e4ee370be110a