ixgbe: Add support for enabling UDP RSS via the ethtool rx-flow-hash command

This patch adds support for enabling or disabling UDP RSS via the
ethtool -N rx-flow-hash command.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>