acpi-cpufreq: De-register CPU notifier and free struct msr on error.

If cpufreq_register_driver() fails we would free the acpi driver
related structures but not free the ones allocated
by acpi_cpufreq_boost_init() function. This meant that as
the driver error-ed out and a CPU online/offline event came
we would crash and burn as one of the CPU notifiers would point
to garbage.

Fixes: cfc9c8ed03e4 (acpi-cpufreq: Adjust the code to use the common boost attribute)
Acked-by: Lukasz Majewski <[e-mail]>
Signed-off-by: Konrad Rzeszutek Wilk <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpufreq/acpi-cpufreq.c

···
 	}
 }
 
-static void __exit acpi_cpufreq_boost_exit(void)
+static void acpi_cpufreq_boost_exit(void)
 {
 	if (msrs) {
 		unregister_cpu_notifier(&boost_nb);
···
 	acpi_cpufreq_boost_init();
 
 	ret = cpufreq_register_driver(&acpi_cpufreq_driver);
-	if (ret)
+	if (ret) {
 		free_acpi_perf_data();
-
+		acpi_cpufreq_boost_exit();
+	}
 	return ret;
 }