ACPI: check battery status on resume for un/plug events during sleep

Add ->resume method to the ACPI battery handler to check
if the battery state has changed during sleep.
If yes, update the ACPI internal data structures
for benefit of /proc/acpi/battery/.

Signed-off-by: Jiri Kosina <jikos@jikos.cz>
Cc: Stefan Seyfried <seife@suse.de>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>