nvmet: cleanup nvmet_execute_identify()

nvmet: cleanup nvmet_execute_identify()

Change the order of the cases in nvmet_execute_identify() main
switch-case to match the NVMe 2.0 specification order as defined in
table 273. This is also the increasing order of CNS values.

While at it, for clarity, make it explicit that identify with cns set
to NVME_ID_CNS_CS_NS does not support NVM command set specific data.

No functional changes are introduced by this cleanup.

Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Tested-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>