i40e: refactor fdir setup function

This function did a lot of unnecessary cpu_to_xxx(foo) and making it
worse, each of these calls caused a lot of line wrapping.

Fix look and feel via a refactor of this function.  No functional
changes.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>