drm/amd/display: Refactor FreeSync module

Remove dependency on internal sink map and instead
use existing stream and plane state

Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
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>