[PATCH] md: make sure /block link in /sys/.../md/ goes to correct devices

If a block_device is a partition, then it's kobject is
  bdev->bd_part->kobj
otherwise (if it is a full device), the kobject is
  bdev->bd_disk->kobj

As md wants back-links to the correct object (whether partition or not), we
need to respect this difference...  (Thus current code shows a link to the
whole device, whether we are using a partition or not, which is wrong).

Signed-off-by: Neil Brown <neilb@suse.de>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>