AArch64: fix even more JIT failures

The last patch corrected some issues, but constant-pool entries had actual
codegen bugs in the large memory model (which MCJIT uses).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187126 91177308-0d34-0410-b5e6-96231b3b80d8