Add force usage and config type for HDMI-CEC system audio mode.

New Usage Type: AUDIO_POLICY_FORCE_FOR_HDMI_SYSTEM_AUDIO
New Config Type: AUDIO_POLICY_FORCE_HDMI_SYSTEM_AUDIO_ENFORCED
When HDMI-CEC system audio mode is enabled, AudioService will
call
 setForceUse(AUDIO_POLICY_FORCE_FOR_HDMI_SYSTEM_AUDIO,
          AUDIO_POLICY_FORCE_HDMI_SYSTEM_AUDIO_ENFORCED);
in order to notify enabled system audio mode, so that
audio policy manager chooses proper output.
When it turns into off, AudioService will call
 setForceUse(AUDIO_POLICY_FORCE_FOR_HDMI_SYSTEM_AUDIO,
          AUDIO_POLICY_FORCE_NONE);

Along with it, add new audio output devic type,
AUDIO_DEVICE_OUT_AUX_LINE, in order to distinguish
line out for headphone and aux output of av device.

Bug: 16305986
Bug: 16002150
Change-Id: Idecdf626737f6635ea3cda638c343260b1661c77