i40e: Add set_pauseparam to ethtool

Add i40e implementation of setpauseparam to ethtool.

Change-ID: Ie7766b2091ec8f934737573c9ffd426081966718
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Jim Young <jamesx.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>