drm/amd/display: Only enable audio if speaker allocation exists

drm/amd/display: Only enable audio if speaker allocation exists

[Why]

In dm_helpers_parse_edid_caps, there is a corner case where no speakers
can be allocated even though the audio mode count is greater than 0.
Enabling audio when no speaker allocations exists can cause issues in
the video stream.

[How]

Add a check to not enable audio unless one or more speaker allocations
exist (since doing this can cause issues in the video stream).

Signed-off-by: Alvin Lee <alvin.lee2@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>