Use fixed volume for HDMI only devices

TV VIM3(L) configurations declaring AUDIO_DEFAULT_OUTPUT hdmi should
enable fixed audio volume as volume should be adjusted by the HDMI
sink.

Test: make TARGET_USE_SAMPLE_LAUNCHER=true TARGET_VIM3L=true
      dumpsys media.audio_flinger signal power is ~ 25 dB higher
Change-Id: Ice6d773dc59ddda1f43215f24335d95adb52090e
2 files changed