block: support pi with extended metadata

The nvme spec allows protection information formats with metadata
extending beyond the pi field. Use the actual size of the metadata field
for incrementing the buffer.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20220303201312.3255347-2-kbusch@kernel.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>