ACPI: thinkpad-acpi: handle HKEY thermal and battery alarms

Handle some HKEY events that are actually firmware alarms.  For
now, we do the simple thing: log specific messages to the log and let
the thinkpad-specific event pass to userspace.

In the future, these events will be migrated to generic notifications
and subsystems.

These alarms are NOT available on all ThinkPads.  E.g. the T43 only
issues 0x6011 and 0x6012.

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