i40e: re-use %*ph specifier to hexdump a data

Instead of using a custom approach change the code to use %*ph format
specifier.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>