s390/qeth: optimize MAC handling in rx_mode callback

In layer2 mode of the qeth driver, MAC address lists
from struct net_device require mapping to the OSA-card.
The existing implementation is inefficient for lists with
more than several MAC addresses, since for every
ndo_set_rx_mode callback it removes all MAC addresses first,
and then registers the current MAC address list.
This patch changes implementation of ndo_set_rx_mode callback
in qeth, only performing hardware registration/removal for
new/deleted addresses. To shorten lookup of MAC addresses
registered addresses are kept in a hashtable instead of a
linear list.

Signed-off-by: Lakhvich Dmitriy <ldmitriy@ru.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Reviewed-by: Eugene Crosser <Eugene.Crosser@ru.ibm.com>
Reviewed-by: Thomas Richter <tmricht@de.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>