[NVPTX] Switch nvptx-use-infer-addrspace to true.

Summary:
This switches us to use a different, more powerful algorithm for address
space inference.  I've tested this locally and it seems to work great.
Once we're more confident in it, we can remove the old pass altogether.

Reviewers: jingyue

Subscribers: llvm-commits, tra, jholewinski

Differential Revision: https://reviews.llvm.org/D23694

llvm-svn: 279317