drm/amd/display: explicit uint64_t casting

explicitly cast uint64_t in div64_u64_rem()

Signed-off-by: vikrant mhaske <vikrant.mhaske@amd.com>
Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>