scsi: qla2xxx: Save frame payload size from ICB

Save frame payload size from init control block.  This field/data is used
to register with switch database.  This allows the init control block temp
buf to be reused.

[mkp: remove unused variable]

Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>