i40e: correct i40e_addr_to_hkey() name in kdoc

Correct name of i40e_addr_to_hkey() in it's kdoc.

kernel-doc -none reports:

 drivers/net/ethernet/intel/i40e/i40e.h:739: warning: expecting prototype for i40e_mac_to_hkey(). Prototype was for i40e_addr_to_hkey() instead

Signed-off-by: Simon Horman <horms@kernel.org>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>