lib: export symbol kobject_move()

drivers/cpufreq/cpufreq.c is already using this function. And now btrfs
needs it as well. Export symbol kobject_move().

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David Sterba <dsterba@suse.cz>