selftests/resctrl: Pass the real number of tests to show_cache_info()

Results include warm-up test which is discarded before passing the sum
to show_cache_info(). show_cache_info() handles this by subtracting one
from the number of tests in divisor. It is a trappy construct to have
sum and number of tests parameters to disagree like this.

A more logical place for subtracting the skipped tests is where the sum
is calculated so move it there. Pass the correct number of tests to
show_cache_info() so it can be used directly as the divisor for
calculating the average.

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>