[PATCH] Driver core: potentially fix use after free in class_device_attr_show

This moves the code to free devt_attr from class_device_del() to
class_dev_release() which is called after the last reference to the
corresponding kobject() is gone.

This allows us to keep the devt_attr alive while the corresponding
sysfs file is open.

Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>