tracing: convert c/p state power tracer to use tracepoints

Convert the c/p state "power" tracer to use tracepoints. Avoids a
function call when the tracer is disabled.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>