[SCSI] qla2xxx: Prevent sending mbx commands from sysfs during isp reset.

The fix prevents application path from sending get-firmware-state mbx command
during as isp reset.

Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>