i40e_get_head needs to be called in multiple files in a further patch,
prepare by moving the function into a header file.
Signed-off-by: NKiran Patil <kiran.patil@intel.com>
Tested-by: NAndrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>