scsi: qla2xxx: Add Serdes support for ISP28XX

This patch adds sysfs node for serdes_version and also cleans up port_speed
display.

Signed-off-by: Joe Carnuccio <joe.carnuccio@cavium.com>
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>