arent.  There's no reason to allow open when its parent has been
deactivated and allowing it is inconsistent with regular sysfs file.
Use sysfs_get_active_two() in bin attribute open function.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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