auth-cfg: Avoid overflow when checking key strength compliance

The enumerator strictly handles pointers to pointers, so passing a
`u_int` is incorrect on 64-bit platforms.

Fixes: 918e92c4c9 ("Support multiple different public key strength types in constraints")

src/libstrongswan/credentials/auth_cfg.c

@@ -1146,8 +1146,9 @@ METHOD(auth_cfg_t, complies, bool,
 		char *key_type DBG_UNUSED;
 
 		e2 = create_enumerator(this);
-		while (e2->enumerate(e2, &t2, &strength))
+		while (e2->enumerate(e2, &t2, &value))
 		{
+			strength = (uintptr_t)value;
 			switch (t2)
 			{
 				default: