drm/amd/display: save and restore mall state when applying minimal transition

[why]
There is a case when we are switching from ODM combine to Subvp where
minimal transition based off subvp state is required. In thise case, we
need to save and restore mall state when applying minimal transition.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Acked-by: Hersen Wu <hersenxs.wu@amd.com>
Signed-off-by: Wenjing Liu <wenjing.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>