AArch64: Temporarily disable AArch64AddressTypePromotion

Temporarily disable AArch64AddressTypePromotion, which was effectively
re-enabled in r212073 and r212075, while I look into PR20188.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212189 91177308-0d34-0410-b5e6-96231b3b80d8