drm/amd/display: Generalize new minimal transition path

Previously the new minimal transition path was only used for windowed
MPO + ODM for plane scaling updates. However, we want to generalize the
transition for all cases whenever a non-seamless transition is detected
(such as for MPO -> SubVP + MPC).

To make this change we add pointers in the plane state, stream, and
pointers in the stream state to the dc_scratch state and backup and
restore these so the minimal transition can take place successfully.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>