sae: Fix Wformat warning

src/sae.c:714:3: warning: format ‘%ld’ expects argument of type ‘long
int’, but argument 6 has type ‘size_t’ [-Wformat=]

src/sae.c

@@ -711,7 +711,7 @@ static void sae_process_anti_clogging(struct sae_sm *sm, const uint8_t *ptr,
 	 * It is suggested that an Anti-Clogging Token not exceed 256 octets
 	 */
 	if (len > 256) {
-		l_error("anti-clogging token size %ld too large, 256 max", len);
+		l_error("anti-clogging token size %zu too large, 256 max", len);
 		return;
 	}