cxgbe: Add support to the base driver for NVMe/TCP PDU offload
- Adds various per-queue counters similar to iSCSI PDU offload as well as a hook in the adapter softc for a reference to the NVMe/TCP softc.
- Instruct the firmware to include a DDP indicator in the status field for NVMe/TCP PDU completion messages. This flag indicates if the payload data for a PDU has been received in the free list or if it was placed directly into a kernel I/O data buffer via DDP.
Sponsored by: Chelsio Communications