R600/SI: Use pseudo instruction for fabs/clamp/fneg

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208478 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Prettier display of input modifiers

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208479 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Fold fabs/fneg into src input modifier

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208480 91177308-0d34-0410-b5e6-96231b3b80d8