[PATCH] bonding: allow bond to use TSO if slaves support it

Add NETIF_F_TSO (NETIF_F_UFO) to BOND_INTERSECT_FEATURES so that it can
be used by a bonding device iff all its slave devices support TSO (UFO).

Signed-off-by: Arthur Kepner <akepner@sgi.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>