scsi: myrs: Fix a double free in myrs_cleanup()

In myrs_cleanup(), cs->mmio_base will be freed twice by iounmap().

Link: https://lore.kernel.org/r/20210311063005.9963-1-lyl2019@mail.ustc.edu.cn
Fixes: 77266186 ("scsi: myrs: Add Mylex RAID controller (SCSI interface)")
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/myrs.c

@@ -2273,12 +2273,12 @@ static void myrs_cleanup(struct myrs_hba *cs)
 	if (cs->mmio_base) {
 		cs->disable_intr(cs);
 		iounmap(cs->mmio_base);
+		cs->mmio_base = NULL;
 	}
 	if (cs->irq)
 		free_irq(cs->irq, cs);
 	if (cs->io_addr)
 		release_region(cs->io_addr, 0x80);
-	iounmap(cs->mmio_base);
 	pci_set_drvdata(pdev, NULL);
 	pci_disable_device(pdev);
 	scsi_host_put(cs->host);