ixgbe: correct function number for some 82598 parts

Some 82598 parts have LAN0 disabled and LAN1 enabled and the LAN ID bits in
Device Status register report the NIC as having only LAN1 as enabled. This
causes ixgbe_set_lan_id_multi_port_pcie() to set bus->func = 1 which is
incorrect.

Force bus->func to 0 when LAN0 is disabled in the EEPROM.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Evan Swanson <evan.swanson@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>