nvme: use the changed namespaces list log to clear ns data changed AENs

Per section 5.2 we need to issue the corresponding log page to clear an
AEN, so for a namespace data changed AEN we need to read the changed
namespace list log.  And once we read that log anyway we might as well
use it to optimize the rescan.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>