drm/amd/display: Make create_stream_for_sink more consistent

We've got a helper function to call dc_create_stream_for_sink and one
other place that calls it directly. Make sure we call the helper
functions always since we need to update a bunch of things in stream and
don't want to miss that.

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>