perf/x86/intel/cstate: Prevent hotplug callback leak

If the pmu registration fails the registered hotplug callbacks are not
removed. Wrong in any case, but fatal in case of a modular driver.

Replace the nonsensical state names with proper ones while at it.

Fixes: 77c34ef1

 ("perf/x86/intel/cstate: Convert Intel CSTATE to hotplug state machine")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org