drm/amd/display: Allow option to use worst-case watermark

use worse case watermark (consider both DCC and VM)
to keep golden consistent regardless of DCC

Signed-off-by: Tony Cheng <tony.cheng@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>