AArch64: don't mask off shift bits when processing JIT relocations.

This should actually make the MCJIT tests pass again on AArch64. I don't know
how I missed their failure before.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187120 91177308-0d34-0410-b5e6-96231b3b80d8