[PATCH] lockdep: annotate pktcdvd natural device hierarchy

The pkt_*_dev functions operate on not-this-blockdevice, and that is
sufficiently checked at setup time.  As a result there is a natural
hierarchy, which needs nesting annotations

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Peter Osterlund <petero2@telia.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>