tools/power turbostat: Clean up add perf/msr counter logic

Increase the code readability by moving the no_perf/no_msr flag and the
cai->perf_name/cai->msr sanity checks into the counter probe functions.

No functional change.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>