nvme: remove nvme_update_formats

Now that the queue is frozen before updating ->lba_shift we can't hit the
invalid references mentioned in the comment any more.  More importantly
this code would not have helped us if the format was changed by another
controller or through implementation defined back channels.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>