AMDGPU: Handle 32-bit address wraparounds for SMRD opcodes

Summary: This fixes GPU hangs with OpenGL bindless handle arithmetic.

Reviewers: arsenm, nhaehnle

Subscribers: kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D51203

llvm-svn: 340959