scsi: qla2xxx: Prevent sysfs access when chip is down

Prevent user from sending commands through sysfs while firmware is not
running or reset is in progress.

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>