rz1000: set serialized flag only if mate interface exists

Setting hwif->serialized makes sense only if the mate interface exists.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/rz1000.c b/drivers/ide/pci/rz1000.c
index dd2583e..0d76af4 100644
--- a/drivers/ide/pci/rz1000.c
+++ b/drivers/ide/pci/rz1000.c
@@ -41,7 +41,8 @@
 		printk(KERN_INFO "%s: disabled chipset read-ahead "
 			"(buggy RZ1000/RZ1001)\n", hwif->name);
 	} else {
-		hwif->serialized = 1;
+		if (hwif->mate)
+			hwif->mate->serialized = hwif->serialized = 1;
 		hwif->drives[0].no_unmask = 1;
 		hwif->drives[1].no_unmask = 1;
 		printk(KERN_INFO "%s: serialized, disabled unmasking "