nvmet: fix Identify Identification Descriptor List handling

The Identification Descriptor List CNS value does not check the CSI
value, so remove the code trying to handle it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>