drm/amd/display: Create fake sink if needed when commit stream

The problem we're trying to fix is this (and similar):
1) X Desktop with single display
2) VT switch
3) Unplug display
4) VT switch back to X
5) re-plug same display

Before this we'd fail at step 4 when trying to create a dc_stream_state
because of a missing sink. This change will fake a sink in this case.

The same scenario applies to S3 resume.

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>