drm/amd/display: Don't report fake sink as connected

This was missed in the previous fake sink change. The fake sink
allows us to enable a pipe with a disconnected display. We
shouldn't report it as connected.

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