RFC: Add WWN in superblock

["Jianpeng Ma" <majianpeng@xxxxxxxxx>]

Hi neil:
	In mailist, many people ask the question about disk order.
But because the reboot or anthor probelm, the disk-name maybe change.
So we can't get disk-order.But if we can add WWN(Now,most harddisk has this attribute),
we can find the orders anything.

Thanks!?韬{.n?????%??檩??w?{.n???{炳盯w???塄}?财??j:+v??????2??璀??摺?囤??z夸z罐?+?????w棹f