fix a wireguard mbuf leak

[YASUOKA Masahiko]

A leak may happens when wgpeer is deleted.

ok?

The state queue should be freeed when wg_peer is destroyed.
diff from IIJ.

Index: sys/net/if_wg.c
===================================================================
RCS file: /disk/cvs/openbsd/src/sys/net/if_wg.c,v
retrieving revision 1.29
diff -u -p -r1.29 if_wg.c
--- sys/net/if_wg.c     3 Aug 2023 09:49:08 -0000       1.29
+++ sys/net/if_wg.c     22 Sep 2023 03:11:47 -0000
@@ -518,6 +518,9 @@ wg_peer_destroy(struct wg_peer *peer)
        taskq_barrier(wg_crypt_taskq);
        taskq_barrier(net_tq(sc->sc_if.if_index));
 
+       if (!mq_empty(&peer->p_stage_queue))
+               mq_purge(&peer->p_stage_queue);
+
        DPRINTF(sc, "Peer %llu destroyed\n", peer->p_id);
        explicit_bzero(peer, sizeof(*peer));
        pool_put(&wg_peer_pool, peer);