drm/amd/display: Wrap dcn301_calculate_wm_and_dlg for FPU.

Mirrors the logic for dcn30. Cue lots of WARNs and some
kernel panics without this fix.

Cc: stable@vger.kernel.org
Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>