hwmon: (applesmc) Properly initialize lockdep attributes

The switch to dynamically allocated sysfs attributes left the
internal lockdep members uninitialized, causing a formal bug.
This patch adds sysfs_attr_init() to the node creation function,
remedying the problem.

Reported-and-tested-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>