aaudio: clean up MMAP volume TODO

onVolumeChanged() passes in a list of channels and an associated
volume for each one.

However, both the sender (AudioFlinger) and the consumer (AAudio)
is not using this efficiently. AudioFlinger simply sets all the
volumes as the same value and AAudio simply uses the first value.

This CL removes the TODO and cleans up the function parameters.

Bug: 220162278
Test: OboeTester
Change-Id: I3d8b1ad7228e02e2db6d776af7f5a618fdf50a53
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index dd278f0..1a3754c 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -10261,20 +10261,10 @@
         } else {
             sp<MmapStreamCallback> callback = mCallback.promote();
             if (callback != 0) {
-                int channelCount;
-                if (isOutput()) {
-                    channelCount = audio_channel_count_from_out_mask(mChannelMask);
-                } else {
-                    channelCount = audio_channel_count_from_in_mask(mChannelMask);
-                }
-                Vector<float> values;
-                for (int i = 0; i < channelCount; i++) {
-                    values.add(volume);
-                }
                 mHalVolFloat = volume; // SW volume control worked, so update value.
                 mNoCallbackWarningCount = 0;
                 mLock.unlock();
-                callback->onVolumeChanged(mChannelMask, values);
+                callback->onVolumeChanged(volume);
                 mLock.lock();
             } else {
                 if (mNoCallbackWarningCount < kMaxNoCallbackWarnings) {