drm/amdgpu: Use metrics data function to get unique_id for Aldebaran

This is abstracted well enough in the get_metrics_data function, so use
the function

Signed-off-by: Kent Russell <kent.russell@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>