x86: PM: Make APM idle driver initialize polling state

Update the APM driver overlooked by commit 1b39e3f8 (cpuidle: Make
drivers initialize polling state) to initialize the polling state like
the other cpuidle drivers modified by that commit to prevent cpuidle
from crashing.

Fixes: 1b39e3f8 (cpuidle: Make drivers initialize polling state)
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: 4.14+ <stable@vger.kernel.org> # 4.14+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/x86/kernel/apm_32.c

@@ -2389,6 +2389,7 @@ static int __init apm_init(void)
 	if (HZ != 100)
 		idle_period = (idle_period * HZ) / 100;
 	if (idle_threshold < 100) {
+		cpuidle_poll_state_init(&apm_idle_driver);
 		if (!cpuidle_register_driver(&apm_idle_driver))
 			if (cpuidle_register_device(&apm_cpuidle_device))
 				cpuidle_unregister_driver(&apm_idle_driver);