[PATCH] initialise mca_bus_type even if !MCA_bus

From: "Randy.Dunlap" <rddunlap@osdl.org>

We need to call mca_system_init() to register MCA bus struct, otherwise
find_mca_adapter() oopses with a NULL ptr dereference.

Fixes this oops reported last week:
	http://marc.theaimsgroup.com/?l=linux-kernel&m=108455738606747&w=2

Thanks to James Bottomley for pointing this out.

arch/i386/kernel/mca.c

@@ -258,16 +258,16 @@ static int __init mca_init(void)
 
 	/* Make sure the MCA bus is present */
 
-	if(!MCA_bus)
-		return -ENODEV;
-
-	printk(KERN_INFO "Micro Channel bus detected.\n");
-
-	if(mca_system_init()) {
+	if (mca_system_init()) {
 		printk(KERN_ERR "MCA bus system initialisation failed\n");
 		return -ENODEV;
 	}
 
+	if (!MCA_bus)
+		return -ENODEV;
+
+	printk(KERN_INFO "Micro Channel bus detected.\n");
+
 	/* All MCA systems have at least a primary bus */
 	bus = mca_attach_bus(MCA_PRIMARY_BUS);
 	if (!bus)