drm/amd/display: Backup and restore plane configuration only on update

[WHY&HOW]
When backing up and restoring plane states for minimal transition
cases, only configuration should be backed up and restored. Information
only relevant to the object/allocation (like refcount) should be
excluded. Also move this interface to dc_plane.h.

Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Dillon Varone <Dillon.Varone@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>