drm/amd/display: Release fake sink

If connector doesn't have a sink, fake sink is created, but
never released as it assumed that its destroyed with the
stream it is used for. But now sink is released before the
stream maintaing refcount consistency.

This way we also avoid assigning anything to connector keeping
all the operation local.

Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>