[AMDGPU] Recognize x & (-1 >> (32 - y)) pattern.

Summary:
D47980 will canonicalize the `x << (32 - y) >> (32 - y)`,
which is the pattern the AMDGPU expects to `x &  (-1 >> (32 - y))`,
which is not recognized by AMDGPU.

Thus, it needs to be recognized, too.

Reviewers: nhaehnle, bogner, tstellar, arsenm

Reviewed By: arsenm

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

Tags: #amdgpu

Differential Revision: https://reviews.llvm.org/D48007

llvm-svn: 334815