[SCSI] cxgb3i: added per-task data to track transmit progress

added per-task struct cxgb3i_task_data to track the data transmiting
progress and the state of the pdus to be transmitted.

Signed-off-by: Karen Xie <kxie@chelsio.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>