nvme: enhance cns version checking

The number of CNS bits in the command is specific to the nvme spec
version compliance. The existing check is not sufficient for possible
CNS values the driver uses that may create confusion between host and
device, so enhance the check to consider the version and desired CNS
value.

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>