hal: Correct the multi-channel output usecase selection

Both Multi-channel output on HDMI and Compress offload playback on
HDMI use cases request for a stream with AUDIO_OUTPUT_FLAG_DIRECT.
The current logic would then result selection MULTI_CH usecase.
Fix this by checking for complete match of flags to select the
use case.

Change-Id: I66df94af6c3b837a6c8054282364e1acf78e6e0f