scsi: cxgb4i: Add support for iSCSI segmentation offload

T5/T6 adapters support iSCSI segmentation offload.

To transmit iSCSI PDUs using ISO driver provides iSCSI header and data
scatterlist to the adapter, adapter forms multiple iSCSI PDUs and transmits
them.

[mkp: checkpatch]

Link: https://lore.kernel.org/r/1593448871-2972-1-git-send-email-varun@chelsio.com


Signed-off-by: Varun Prakash <varun@chelsio.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>