This patch implements a feature change which allows using ethtool to set
RSS hash opts using less than four parameters if desired.

Change-ID: I0fbb91255d81e997c456697c21ac39cc9754821b
Signed-off-by: NCarolyn Wyborny <carolyn.wyborny@intel.com>
Signed-off-by: NKiran Patil <kiran.patil@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>