selftests/resctrl: Fix wrong format specifier

Compiling resctrl selftest after adding a __printf() attribute to
ksft_print_msg() exposes -Wformat warning in show_cache_info().
The format specifier used expects a variable of type int but a long
unsigned int variable is passed instead.

Change the format specifier to match the passed variable.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>