Don't perform gvn on instructions with other_side_effects().

cranelift/filetests/simple_gvn/reject.cton

@@ -0,0 +1,11 @@
+test simple-gvn
+
+function %other_side_effects(i32) -> i32 {
+ebb0(v0: i32):
+   regmove v0, %10 -> %20
+   regmove v0, %10 -> %20
+   regmove v0, %20 -> %10
+; check: regmove v0, %10 -> %20
+; check: regmove v0, %10 -> %20
+    return v0
+}