The 'TSAS' value is only defined for TCP and RDMA, but returning
'reserved' for undefined values tricked nvmetcli to try to write
'reserved' when restoring from a config file. This caused an error
and the configuration would not be applied.

Fixes: 3f123494 ("nvmet: make TCP sectype settable via configfs")
Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>