selftests/resctrl: Move CAT/CMT test global vars to function they are used in

CAT and CMT tests have count_of_bits, long_mask, cbm_mask, and
cache_size global variables that can be moved into the sole using
function.

Make the global variables local variables of the relevant function to
scope them better.

While at it, move cache_size initialization into the declaration line.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Shaopeng Tan (Fujitsu) <tan.shaopeng@fujitsu.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>