ACPI: fan: Initialize performance state sysfs attribute

The following warning is reported if lock debugging is enabled.

DEBUG_LOCKS_WARN_ON(1)
WARNING: CPU: 1 PID: 1 at kernel/locking/lockdep.c:4617 lockdep_init_map_waits+0x141/0x222
...
Call Trace:
 __kernfs_create_file+0x7a/0xd8
 sysfs_add_file_mode_ns+0x135/0x189
 sysfs_create_file_ns+0x70/0xa0
 acpi_fan_probe+0x547/0x621
 platform_drv_probe+0x67/0x8b
 ...

Dynamically allocated sysfs attributes need to be initialized to avoid
the warning.

Fixes: d19e470b ("ACPI: fan: Expose fan performance state information")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: 5.6+ <stable@vger.kernel.org> # 5.6+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>