softap: allow output of multicast frames.

Multicast frames were being dropped by ieee80211_output_pbuf. It appears to look
up the destination address using cnx_node_search which only has an entry for the
broadcast address (all ones). This patch modifies cnx_node_search to return the
broadcast cnx_node for the multicast addresses too.

This is needed to support services such as mDNS on the softap interface.

open_esplibs/libnet80211/wl_cnx.c

@@ -192,6 +192,11 @@ struct sdk_cnx_node *sdk_cnx_node_search(uint8_t mac[6])
 
     struct sdk_cnx_node **cnx_nodes = sdk_g_ic.v.softap_netif_info->cnx_nodes;
 
+    /* Multicast addresses */
+    if (mac[0] & 0x01) {
+        return cnx_nodes[0];
+    }
+
     int i = 0;
     do {
         struct sdk_cnx_node *cnx_node = cnx_nodes[i];