drm/amd/display: avoid crash and add z8_marks related in dml

[why]
add dml1 used calculate_wm_and_dlg function pointer check to prevent crash.
add z8 watermarks to struct for later asic use

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Stylon Wang <stylon.wang@amd.com>
Signed-off-by: Charlene Liu <charlene.liu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>