drm/amd/display: Removed z10 save after dsc disable

[Why & How]
Z10 save is done during PSR and bootup.
DSC disable does not need to save for Z10.

Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Agustin Gutierrez Sanchez <agustin.gutierrez@amd.com>
Signed-off-by: Jake Wang <haonan.wang2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>