i40evf: add FW version to ethtool info

Customers reported that the firmware version information from i40evf
is unlike that of ixgbevf and was causing problems with their scripts.
To resolve this, populate the field to align with ixgbevf.

Change-ID: I9f4e24f6a76cd819bbe07087aab2b74f715ec103
Reported-by: Sourav Chatterjee <sourav.chatterjee@intel.com>
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Jim Young <james.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>