cpufreq: Init completion before kobject_init_and_add()

In cpufreq_policy_alloc(), it will call uninitialed completion in
cpufreq_sysfs_release() when kobject_init_and_add() fails. And
that will cause a crash such as the following page fault in complete:

BUG: unable to handle page fault for address: fffffffffffffff8
[..]
RIP: 0010:complete+0x98/0x1f0
[..]
Call Trace:
kobject_put+0x1be/0x4c0
cpufreq_online.cold+0xee/0x1fd
cpufreq_add_dev+0x183/0x1e0
subsys_interface_register+0x3f5/0x4e0
cpufreq_register_driver+0x3b7/0x670
acpi_cpufreq_init+0x56c/0x1000 [acpi_cpufreq]
do_one_initcall+0x13d/0x780
do_init_module+0x1c3/0x630
load_module+0x6e67/0x73b0
__do_sys_finit_module+0x181/0x240
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 4ebe36c94aed ("cpufreq: Fix kobject memleak")
Signed-off-by: Yongqiang Liu <[e-mail]>
Acked-by: Viresh Kumar <[e-mail]>
Cc: 5.2+ <[e-mail]> # 5.2+
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpufreq/cpufreq.c

···
 	if (!zalloc_cpumask_var(&policy->real_cpus, GFP_KERNEL))
 		goto err_free_rcpumask;
 
+	init_completion(&policy->kobj_unregister);
 	ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq,
 				   cpufreq_global_kobject, "policy%u", cpu);
 	if (ret) {
···
 	init_rwsem(&policy->rwsem);
 	spin_lock_init(&policy->transition_lock);
 	init_waitqueue_head(&policy->transition_wait);
-	init_completion(&policy->kobj_unregister);
 	INIT_WORK(&policy->update, handle_update);
 
 	policy->cpu = cpu;