nvme: Add the DHCHAP maximum HD IDs

nvme: Add the DHCHAP maximum HD IDs

In preperation for using DHCHAP length in upcoming host and target
patches let's add the hash and diffie-hellman ID length macros.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Yunje Shin <ioerts@kookmin.ac.kr>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>