Support MSD patches with channel index masks

To support MSD patch channel count flexibility, as well as to remove
the need for input & output position mask matching, support MSD audio
patches using channel index masks.

Test: 1. patch channel index mask 6 between MSD and primary HAL
      2. atest audiopolicy_tests
Change-Id: I89f29457579d297df7b9908b0cd6df7896440930