USB: use %*ph specifier in uss720 driver

There is a %*ph specifier that allows to dump small buffers. This patch
converts the code to use the specifier.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>