hw/nvme: fix endianess conversion and add controller list

Add the controller identifiers list CNS 0x13, available list of ctrls
in NVM Subsystem that may or may not be attached to namespaces.

In Identify Ctrl List of the CNS 0x12 and 0x13 no endian conversion
for the nsid field.

These two CNS values shows affect when there exists a Subsystem.
Added condition if there is no Subsystem return invalid field in
command.

Signed-off-by: Gollu Appalanaidu <anaidu.gollu@samsung.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>