Revert "[Reassociate] Canonicalize negative constants out of expressions."

This reverts commit r221171.

It performs this invalid transformation:
-  %div.i = urem i64 -1, %add
-  %sub.i = sub i64 -2, %div.i
+  %div.i = urem i64 1, %add
+  %sub.i1 = add i64 %div.i, -2