nvme-fabrics: Add type of service (TOS) configuration

TOS is user-defined and needs to be configured via nvme-cli.
It must be set before initiating any traffic and once set the TOS
cannot be changed.

Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>