Use ParseFnAttributeValuePairs instead of ParseOptionalFuncAttrs 

The functionality of ParseOptionalFuncAttrs was there in
ParseFnAttributeValuePairs. So just use that instead.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174686 91177308-0d34-0410-b5e6-96231b3b80d8