scsi: qla2xxx: Prevent SysFS access when chip is down

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

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>