force g711 test to match 1-channel sample data

special case the g711 test to know that it is a 1-channel input.
Test case itself can't infer the channel count from the g711 stream
since there is no header/control info within the g711 stream.

Bug: 140773833
Test: vts-tradefed run vts --module VtsHalMediaC2V1_0Host
Change-Id: I9ac1f4d3ee0ccc42ffc8c199fcb88dc5c7122c0e