tools/power turbostat: track thread ID in cpu_topology

The code can be simplified if the cpu_topology *cpus tracks the thread
IDs.  This removes an additional file lookup and simplifies the counter
initialization code.

Add thread ID to cpu_topology information and cleanup the counter
initialization code.

v2: prevent thread_id from being overwritten

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Len Brown <len.brown@intel.com>