super_1_sync only updates fields in the superblock that might have changed.

'raid_disks' and 'size' could have changed, but this information doesn't get
updated....  until this patch.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>