drm/amd/display: Silence type mismatch warning

drm/amd/display: Silence type mismatch warning

[Why&How]
Resolve type mismatch warnings by ensuring loop counters and compared
values use matching unsigned types (size_t or int) in array iteration.

Reviewed-by: Aric Cyr <aric.cyr@amd.com>
Signed-off-by: Gaghik Khachatrian <gaghik.khachatrian@amd.com>
Signed-off-by: Ivan Lipski <ivan.lipski@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>