be2net: Avoid redundant addition of mac address in HW

If a mac address is added to the uc_list and later the same mac address
is added via ndo_set_mac_address() or vice versa, the driver does not
detect this condition and tries to add it again. This results in a mac
address collision error when the FW rejects it.

Fix this by checking if the given mac address is present in uc_list while
setting the device mac address and vice versa. Similarly skip deletion if
the address is still in use in the other form.

Signed-off-by: Suresh Reddy <Suresh.Reddy@broadcom.com>
Signed-off-by: Sathya Perla <sathya.perla@broadcom.com>
Signed-off-by: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>