nvmf_proto.h: Add additional types and constants from the 1.1 spec

• Add opcode, command structure, and new error code for Disconnect fabrics opcode.

• Add a generic struct nvmf_fabric_command.

• Add constants for special controller ID values.

• Add constants for the cattr field in the Connect command and the default value for the kato field in the Connect command.

• Add constants for the offset of controller properties (Fabrics version of controller registers).

Reviewed by: imp
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D44705