drm/amd/display: correct data type

[Why]
We should use int for counting variable

[How]
Change type from bool to uint32_t

Signed-off-by: Raymond Yang <rayyang@amd.com>
Acked-by: Bindu Ramamurthy <bindu.r@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>