AArch64: Fix XSeqPairs/WSeqPairs problems

- Fix spill/reloads of XSeqPairs failing with vregs (only physregs
  worked correctly)
- Add missing spill/reload code for WSeqPairs class

Differential Revision: https://reviews.llvm.org/D52761

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@343799 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed