drm/amd/display: Fix dml2_0 narrowing boundaries

drm/amd/display: Fix dml2_0 narrowing boundaries

[Why] drm/amd/display dml2_0 code had implicit narrowing conversions reported by
a warning in timing, watermark, and translation paths.

[How] Apply explicit boundary casts for intentional narrowing, preserve wider
intermediate math, and use wider timing intermediates where required for safe
range handling.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Gaghik Khachatrian <gaghik.khachatrian@amd.com>
Signed-off-by: Chenyu Chen <chen-yu.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>