net: sockets_service: Always clear old events when registering

Clear all previous events when register is called a second time. This is
the same behavior as before, if the call happens with `len` equal or
greater then the previous call but in the case if `len` is less then the
first call, now, all events are cleared. This is more predictable behavior.

Signed-off-by: Cla Mattia Galliard <cla-mattia.galliard@zuehlke.com>

Author: clamattia

subsys/net/lib/sockets/sockets_service.c

@@ -71,9 +71,9 @@ int z_impl_net_socket_service_register(const struct net_socket_service_desc *svc
 		goto out;
 	}
 
-	if (fds == NULL) {
-		cleanup_svc_events(svc);
-	} else {
+	cleanup_svc_events(svc);
+
+	if (fds != NULL) {
 		if (len > svc->pev_len) {
 			NET_DBG("Too many file descriptors, "
 				"max is %d for service %p",