audio: Add AUDIO_CHANNEL_OUT_22POINT2 constant

24 channel configuration for immersive audio

See new value in system/media/audio/audio-hal-enums.h.
Define the same enum to HALv7 and update getChannelCount().

Test: atest android.hardware.audio.common@7.0-util_tests
Bug: 185530406
Change-Id: I8dc5e6c504049908fef157b11ffa043ecaeacaf9