frameworks/av: enable voip flag based on channelcount

voip flag should be enabled based on channelcount instead of
channelmask. Some of voip apps like viber may not use
AUDIO_CHANNEL_OUT_MONO but still configures to single channel
like by using AUDIO_CHANNEL_OUT_FRONT_CENTER.

Change-Id: I3f69a5c50b6e1bb9336e08eb9619e15de2d8a532
CRs-Fixed: 511713