drm/amd/display: Add variable refresh rate parameters to DC structures

Time stamping will be part of surface, and will be updated when address is flipped.
FreeSync parameters will be attached to stream, as it adjusts the timing dynamically.

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