[BRIDGE]: recompute features when adding a new device

We must recompute bridge features everytime the list of underlying 
devices changes, or we might end up with features that are not
supported by all devices (eg. NETIF_F_TSO)
This patch adds the missing recompute when adding a device to the bridge.

Signed-off-by: Olaf Rempel <razzor@kopf-tisch.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index defcf6a..975abe2 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -366,6 +366,7 @@
 
 		spin_lock_bh(&br->lock);
 		br_stp_recalculate_bridge_id(br);
+		br_features_recompute(br);
 		if ((br->dev->flags & IFF_UP) 
 		    && (dev->flags & IFF_UP) && netif_carrier_ok(dev))
 			br_stp_enable_port(p);