s390/cpum_cf: Fix missing cpu hotplug notifier transition

The cpumf_pmu_notfier() hotplug callback lacks handling of the
CPU_DOWN_FAILED case. That means, if CPU_DOWN_PREPARE failes, the PMC
of the CPU is not setup again.

Add handling for CPU_DOWN_FAILED transition to setup the PMC of the
CPU.
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/perf_cpum_cf.c

@@ -670,6 +670,7 @@ static int cpumf_pmu_notifier(struct notifier_block *self, unsigned long action,
 
 	switch (action & ~CPU_TASKS_FROZEN) {
 	case CPU_ONLINE:
+	case CPU_DOWN_FAILED:
 		flags = PMC_INIT;
 		smp_call_function_single(cpu, setup_pmc_cpu, &flags, 1);
 		break;