freebsd11_wlan: Add ieee80211_realign.

It is technically "used", but only in blocks that evaluate to false via
preprocessor macros, and so it was usually optimized out completely.
This is not the case for the debug build however, so the lack of it
broke that.

src/libs/compat/freebsd11_wlan/net80211/ieee80211_haiku.cpp

@@ -485,6 +485,46 @@ ieee80211_flush_ifq(struct ifqueue* ifq, struct ieee80211vap* vap)
 }
 
 
+#ifndef __NO_STRICT_ALIGNMENT
+/*
+ * Re-align the payload in the mbuf.  This is mainly used (right now)
+ * to handle IP header alignment requirements on certain architectures.
+ */
+struct mbuf *
+ieee80211_realign(struct ieee80211vap *vap, struct mbuf *m, size_t align)
+{
+	int pktlen, space;
+	struct mbuf *n;
+
+	pktlen = m->m_pkthdr.len;
+	space = pktlen + align;
+	if (space < MINCLSIZE)
+		n = m_gethdr(M_NOWAIT, MT_DATA);
+	else {
+		n = m_getjcl(M_NOWAIT, MT_DATA, M_PKTHDR,
+		    space <= MCLBYTES ?     MCLBYTES :
+#if MJUMPAGESIZE != MCLBYTES
+		    space <= MJUMPAGESIZE ? MJUMPAGESIZE :
+#endif
+		    space <= MJUM9BYTES ?   MJUM9BYTES : MJUM16BYTES);
+	}
+	if (__predict_true(n != NULL)) {
+		m_move_pkthdr(n, m);
+		n->m_data = (caddr_t)(ALIGN(n->m_data + align) - align);
+		m_copydata(m, 0, pktlen, mtod(n, caddr_t));
+		n->m_len = pktlen;
+	} else {
+		IEEE80211_DISCARD(vap, IEEE80211_MSG_ANY,
+		    mtod(m, const struct ieee80211_frame *), NULL,
+		    "%s", "no mbuf to realign");
+		vap->iv_stats.is_rx_badalign++;
+	}
+	m_freem(m);
+	return n;
+}
+#endif /* !__NO_STRICT_ALIGNMENT */
+
+
 int
 ieee80211_add_callback(struct mbuf* m,
 	void (*func)(struct ieee80211_node*, void*, int), void* arg)