Check if AC state has changed across resume and notify userspace if so.

Fixes "[2.6.24-rc1 regression] AC adapter state does not change after resume"
Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Tested-by: Andrey Borzenkov <arvidjaar@mail.ru>
Cc: Len Brown <lenb@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>