OLPC: Use %*ph specifier instead of passing direct values

The %*ph specifier allows to dump small buffers in hex format. Let's use it
instead of passing direct values via stack.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Paul Fox <pgf@laptop.org>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>