[SystemZ] Use valid base/index regs for inline asm

Summary:
Inline asm memory constraints can have the base or index register be assigned
to %r0 right now. Make sure that we assign only ADDR64 registers to the base
and index.

Reviewers: uweigand

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23367

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279157 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed