drm/amd/display: Disable audio stream only if it's currently enabled

[Why]
Previously there were 2 consecutive calls being made to disable
audio stream. The first one disabled the audio stream, and the second
one went through and also tried to disable the audio stream causing
BACO entry issues due to the ASIC appearing busy.

[How]
1. Add a status field to the audio struct which stores enabled/disabled
info
2. In the calls to enable/disable audio stream check if we're already
in the desired state before executing the function

Signed-off-by: Eryk Brol <eryk.brol@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>