sync/atomic: implement LoadUint32
sync/atomic: implement LoadUint32

Somehow it was missing for no reason.

Change-Id: Iad24b65dbe3e8cc4d9b06fe40bd01262897866d7

4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go