AArch64: Actually do address type promotion

AArch64AddressTypePromotion was doing nothing because it was using the
old semantics of `Use` and `uses()`, when it really wanted to get at the
`users()`.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212073 91177308-0d34-0410-b5e6-96231b3b80d8