qlcnic: support mac learning

Device eswitch need to configure with VM's mac address.
Hypervisor doesn't provide any utility/callbacks to get VM's mac address.
Unicast mac address filter improves performance and also provide
packet loopback capability i.e communication between VM.

Above features is by default off, can be turned on with module parameter
'mac_learn'.

Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>