Revert "FunctionAttrs: Merge attributes once instead of doing it for every argument."

It doesn't work as I intended it to.  This reverts commit r184638.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184641 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed