ACPI: thinkpad-acpi: add poll() support to some sysfs attributes

Implement poll()/select() support through sysfs_notify() for some key
attributes which userspace might want to poll() or select() on.

In order to let userspace know poll()/select() support is available for an
attribute, the thinkpad-acpi sysfs interface version is also bumped up.
Further changes that add poll()/select() capabilities to any pre-existing
attributes will also increment the sysfs interface version.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>