Add information about configuring perf events using libpfm4
Add information about configuring perf events using libpfm4

Signed-off-by: Katarzyna Kujawa <6d81612c80214d850c10c80be3c4dcdb2935414e@intel.com>

linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor