tools/power/x86/intel_pstate_tracer: make tracer as a module

Make intel_pstate_tracer as a module. Other trace event can import
this module to analyze their trace data.

Signed-off-by: Jinzhou Su <Jinzhou.Su@amd.com>
Acked-by: Doug Smythies <dsmythies@telus.net>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>