Code clean for audioflinger

Cleaning compile warnings:
1. For "variable 'XX' set but not used":
   Remove the variables which are obviously not used;
   Add "[[maybe_unused]]" to variable declaration of the ones
       which are potentially used.
2. For "unused parameter 'XX'":
   Add "[[maybe_unused]]" to the unused function parameters.

Test: mmm frameworks/av/services/audioflinger, presubmit check.

Change-Id: I6bd6fa9a57de93f5387e1ad76342f0a0b0ac28ed
Signed-off-by: Jing Mike <jingyangliu@eswincomputing.com>
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index b72348a..37b8fe8 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -3293,7 +3293,7 @@
 }
 
 void AudioFlinger::PlaybackThread::threadLoop_removeTracks(
-        const Vector< sp<Track> >& tracksToRemove)
+        [[maybe_unused]] const Vector< sp<Track> >& tracksToRemove)
 {
     // Miscellaneous track cleanup when removed from the active list,
     // called without Thread lock but synchronized with threadLoop processing.
@@ -3304,8 +3304,6 @@
             addBatteryData(IMediaPlayerService::kBatteryDataAudioFlingerStop);
         }
     }
-#else
-    (void)tracksToRemove; // suppress unused warning
 #endif
 }
 
@@ -5829,7 +5827,7 @@
     }
 
     // Push the new FastMixer state if necessary
-    bool pauseAudioWatchdog = false;
+    [[maybe_unused]] bool pauseAudioWatchdog = false;
     if (didModify) {
         state->mFastTracksGen++;
         // if the fast mixer was active, but now there are no fast tracks, then put it in cold idle
@@ -7570,7 +7568,7 @@
     size_t numCounterOffers = 0;
     const NBAIO_Format offers[1] = {Format_from_SR_C(mSampleRate, mChannelCount, mFormat)};
 #if !LOG_NDEBUG
-    ssize_t index =
+    [[maybe_unused]] ssize_t index =
 #else
     (void)
 #endif
@@ -7621,7 +7619,7 @@
         Pipe *pipe = new Pipe(pipeFramesP2, format, pipeBuffer);
         const NBAIO_Format offers[1] = {format};
         size_t numCounterOffers = 0;
-        ssize_t index = pipe->negotiate(offers, 1, NULL, numCounterOffers);
+        [[maybe_unused]] ssize_t index = pipe->negotiate(offers, 1, NULL, numCounterOffers);
         ALOG_ASSERT(index == 0);
         mPipeSink = pipe;
         PipeReader *pipeReader = new PipeReader(*pipe);
@@ -9077,7 +9075,8 @@
     audio_format_t reqFormat = mFormat;
     uint32_t samplingRate = mSampleRate;
     // TODO this may change if we want to support capture from HDMI PCM multi channel (e.g on TVs).
-    audio_channel_mask_t channelMask = audio_channel_in_mask_from_count(mChannelCount);
+    [[maybe_unused]] audio_channel_mask_t channelMask =
+                                audio_channel_in_mask_from_count(mChannelCount);
 
     AudioParameter param = AudioParameter(keyValuePair);
     int value;