AMDGPU: Select 64-bit {ADD,SUB}{C,E} nodes

Summary:
This will be used for 64-bit MULHU, which is in turn used for the 64-bit
divide-by-constant optimization (see D24822).

Reviewers: arsenm, tstellarAMD

Subscribers: kzhuravl, wdng, yaxunl, llvm-commits, tony-tye

Differential Revision: https://reviews.llvm.org/D25289

llvm-svn: 284224