ixgbevf: Add X540 VF device support to the ixgbevf driver

The X540 introduces a new Virtual Function device ID so that the X540
VF device can be distinguished from the 82599 VF device.  The X540 VF
device will have additional capability over the 82599 VF device so it
is necessary to be able to discern the difference.

Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>