cpufreq: Fix get_cpu_device() failure in add_cpu_dev_symlink()

cpufreq: Fix get_cpu_device() failure in add_cpu_dev_symlink()

When I hot added a CPU, I found 'cpufreq' directory was not created
below /sys/devices/system/cpu/cpuX/.

It is because get_cpu_device() failed in add_cpu_dev_symlink().

cpufreq_add_dev() is the .add_dev callback of a CPU subsys interface.
It will be called when the CPU device registered into the system.
The call chain is as follows:

  register_cpu()
  ->device_register()
   ->device_add()
    ->bus_probe_device()
     ->cpufreq_add_dev()

But only after the CPU device has been registered, we can get the
CPU device by get_cpu_device(), otherwise it will return NULL.

Since we already have the CPU device in cpufreq_add_dev(), pass
it to add_cpu_dev_symlink().

I noticed that the 'kobj' of the CPU device has been added into
the system before cpufreq_add_dev().

Fixes: c7eebc431973 ("cpufreq: Fix creation of symbolic links to policy directories")
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>