net/bonding: Enable IP multicast for bonding IPoIB devices

Allow to enslave devices when the bonding device is not up. Over the discussion
held at the previous post this seemed to be the most clean way to go, where it
is not expected to cause instabilities.

Normally, the bonding driver is UP before any enslavement takes place.
Once a netdevice is UP, the network stack acts to have it join some multicast groups
(eg the all-hosts 224.0.0.1). Now, since ether_setup() have set the bonding device
type to be ARPHRD_ETHER and address len to be ETHER_ALEN, the net core code
computes a wrong multicast link address. This is b/c ip_eth_mc_map() is called
where for multicast joins taking place after the enslavement another ip_xxx_mc_map()
is called (eg ip_ib_mc_map() when the bond type is ARPHRD_INFINIBAND)

Signed-off-by: Moni Shoua <monis at voltaire.com>
Signed-off-by: Or Gerlitz <ogerlitz at voltaire.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>