basic: make check-pointer-deref clean

Add the needed assert changes to make the code clean
for the new check-pointer-deref script.

Note that for `_cmp()` functions its a bit of a question
if we want `assert()` or `POINTER_MAY_BE_NULL()` here. The
former is more correct but it adds a (small) runtime hit. If
we use POINTER_MAY_BE_NULL() it is compiled out but strictly
speaking it is wrong (so at least we would need a comment).

src/basic/ordered-set.c

@@ -9,6 +9,8 @@
 #include "strv.h"
 
 int ordered_set_ensure_allocated(OrderedSet **s, const struct hash_ops *ops) {
+        assert(s);
+
         if (*s)
                 return 0;
 
@@ -22,6 +24,8 @@ int ordered_set_ensure_allocated(OrderedSet **s, const struct hash_ops *ops) {
 int ordered_set_ensure_put(OrderedSet **s, const struct hash_ops *ops, void *p) {
         int r;
 
+        assert(s);
+
         r = ordered_set_ensure_allocated(s, ops);
         if (r < 0)
                 return r;