drm/amd/display: Fix narrowing boundaries in dml

drm/amd/display: Fix narrowing boundaries in dml

[Why]
DML code paths include implicit integer narrowing at protocol and
storage boundaries. Making these boundaries explicit improves clarity
and reduces warning noise while preserving behavior.

[How]
Apply explicit C-style casts at intentional narrowing boundaries
across DML calculation, mode support, RQ/DLG, wrapper, and DSC
helper paths.
Keep intermediate arithmetic in natural-width types where practical,
with minor type-consistency cleanups where needed. Add explicit
boundary casts for intentional narrowing and keep intermediate math
in wider types where practical, with small type-consistency cleanups
to maintain behavior and readability.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Gaghik Khachatrian <gaghik.khachatrian@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>