enic: Add ndo_set_rx_mode support for enic vnics

Add ndo_set_rx_mode support to register unicast and multicast
address filters for enic devices

Signed-off-by: Roopa Prabhu <roprabhu@cisco.com>
Signed-off-by: Vasanthy Kolluri <vkolluri@cisco.com>
Signed-off-by: David Wang <dwang2@cisco.com>
Signed-off-by: Christian Benvenuti <benve@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>