[SCSI] qla2xxx: Clear options-flags while issuing stop-firmware mbx command.

Not clearing the options flags in mbx1 could lead the firmware
into interpreting old data in mbx1 through mbx8.  This could
lead to inadvertent DMA read/write operations to stale memory.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>