bnx2x: Proper netdev->ndo_set_rx_mode() implementation.

Completed the bnx2x_set_rx_mode() to a proper netdev->ndo_set_rx_mode
implementation:
 - Added a missing configuration of a unicast MAC addresses list.
 - Changed bp->dma_lock from being a mutex to a spinlock as long as it's taken
under netdev->addr_list_lock now.

Signed-off-by: Vladislav Zolotarov <vladz@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>