R600/SI: Don't display GDS bit for read2

This isn't displayed for any other instructions anymore,
and isn't ever used.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214523 91177308-0d34-0410-b5e6-96231b3b80d8
Make getNamedOperandIdx readonly

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214524 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Cleanup test

Remove -CHECKs, use multiple prefixes, name values,
also test the @llvm.fabs version

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214525 91177308-0d34-0410-b5e6-96231b3b80d8