scsi: qla2xxx: Added change to enable ZIO for FC-NVMe devices

Add support to the driver to set the exchange threshold value for
the number of outstanding AENs.

Signed-off-by: Duane Grigsby <duane.grigsby@cavium.com>
Signed-off-by: Darren Trapp <darren.trapp@cavium.com>
Signed-off-by: Anil Gurumurthy <anil.gurumurthy@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>