scsi: qla2xxx: Add support for setting port speed

This patch adds sysfs node

1. There is a new sysfs node port_speed
2. The possible values are 2(Auto neg), 8, 16, 32
3. A value outside of the above defaults to Auto neg
4. Any update to the setting causes a link toggle
5. This feature is currently only for ISP27xx

Signed-off-by: Anil Gurumurthy <agurumurthy@marvell.com>
Signed-off-by: Quinn Tran <qtran@marvell.com>
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>