Update AudioFlinger comments
Update AudioFlinger comments

Add comments to enum mixer_state
Note side-effect of lockEffectChains_l
Fix a typo

Change-Id: Ibd51678bac2193201cbcbe081ff5664046fbc494

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base