InstSimplify: Don't allow (x srem y) urem y -> x srem y

Let's consider the case where:
%x i16 = 32768
%y i16 = 384

%x srem %y = 65408
(%x srem %y) urem %y = 128

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217939 91177308-0d34-0410-b5e6-96231b3b80d8