e1000e: provide MAC-family-specific function to set LAN ID

Provide MAC-specific function pointer to determine the LAN ID (PCI func).
The LAN ID is used internally by the driver to determine which h/w lock
to use to protect accessing the PHY on ESB2 as well as help to determine
the alternate MAC address on some parts.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>