drm/amdgpu: update algorithm of umc uncorrectable error counting

remove the check of ErrorCodeExt

v2: refine the if condition for ue counting

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Dennis Li <dennis.li@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>