[AMDGPU] Rename pass "isel" to "amdgpu-isel"

Summary: The AMDGPU target specific pass "isel" is a misleading name.

Reviewers: tstellar, echristo, javed.absar, arsenm

Reviewed By: arsenm

Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D52759

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@343659 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed