i40e: fix i40e_phy_type_to_ethtool function header

The function header erroneously listed 'phy_types' as a parameter.  The
correct parameter is 'pf'.

Signed-off-by: Alan Brady <alan.brady@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>