Revert "Revert "Rename AudioGain.useInChannelMask -> isInput""

This reverts commit 05399f489aece403775f34cd2c2233243e2d5654.

This is done for consistency with other data structures
and conversion functions.

Bug: 188932434
Test: atest audiofoundation_parcelable_test
Change-Id: Ie98f6063625295c6796c49fdb09107d66546814f
5 files changed