drm/amd/display: Fix FP start/end for dcn30_internal_validate_bw.

It calls populate_dml_pipes which uses doubles to initialize the
scale_ratio_depth params. Mirrors the dcn20 logic.

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