hwmon: (i5k_amb) Fix sysfs attribute for lockdep

i5k_amb.ko uses dynamically allocated memory (by kmalloc) for
attributes passed to sysfs. So, sysfs_attr_init() should be called
for working happy with lockdep.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: stable@kernel.org [2.6.34 only]