i40evf: update i40evf.txt with new content

The addition of the AVF and virtchnl code to the i40evf driver
means we should update the i40evf.txt file with the most up to date
information.

It seems this file hasn't been updated in a while, so the
changes cover a little more than just AVF, but it's all only
in the i40evf.txt.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>