drm/amd/display: Call update_stream_signal directly from amdgpu_dm

There's no good place in DC to cover all place where stream signal should
be updated. update_stream_signal depends on timing which comes from DM.

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>