iavf: Replace __FUNCTION__ with __func__

__FUNCTION__ exists only for backwards compatibility reasons with old
gcc versions. Replace it with __func__.

Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>