Update comment

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214100 91177308-0d34-0410-b5e6-96231b3b80d8
R600/SI: Make argument loads invariant

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214101 91177308-0d34-0410-b5e6-96231b3b80d8