cpufreq: Remove CPU hotplug callbacks only if they were initialized

Since CPU hotplug callbacks are requested for CPUHP_AP_ONLINE_DYN state,
successful callback initialization will result in cpuhp_setup_state()
returning a positive value. Therefore acpi_cpufreq_online being zero
indicates that callbacks have not been installed.

This means that acpi_cpufreq_boost_exit() should only remove them if
acpi_cpufreq_online is positive. Trying to call
cpuhp_remove_state_nocalls(0) will cause a BUG().

Signed-off-by: Boris Ostrovsky <[e-mail]>
Reviewed-by: Thomas Gleixner <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpufreq/acpi-cpufreq.c

···
 
 static void acpi_cpufreq_boost_exit(void)
 {
-	if (acpi_cpufreq_online >= 0)
+	if (acpi_cpufreq_online > 0)
 		cpuhp_remove_state_nocalls(acpi_cpufreq_online);
 }