AudioMixer: recreate Resampler if the track channel count has changed

the Resampler is recreated only if mixer channel count has changed.
I removed the criteria since resampler need recreation when
track channel count has changed.
This issue is due to the previous resampler still working with
the previous channel mask settings.
Test: self-tested more then 50 times when a voice call ended
          and there is an incoming Skype/LINE ringtone.
Bug: 78199280

Change-Id: I042fb9214d07f198704cef3c96bf290c7d203461