[802.11] Fix memory leak on unsuccessful probes

When a probe found no results, the list head of beacons would not be
freed, leaking 16 bytes of memory per probe.

Signed-off-by: Michael Brown <mcb30@etherboot.org>

src/net/80211/net80211.c

 		DBGC ( ctx->dev, "802.11 %p probe: found nothing for '%s'\n",
 		       ctx->dev, ctx->essid );
 
-	if ( ! list_empty ( ctx->beacons ) )
-		net80211_free_wlanlist ( ctx->beacons );
+	net80211_free_wlanlist ( ctx->beacons );
 
 	net80211_keep_mgmt ( ctx->dev, ctx->old_keep_mgmt );