i40evf: add new fields to store user configuration of RSS

This patch adds new fields to i40e_vsi to store user configured
RSS config data and code to use it.

Change-ID: Ic5d3db8d9df52182b560248f8cdca9c5c7546879
Signed-off-by: Helin Zhang <helin.zhang@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>