[PATCH] fix presto_get_sb() return value and oops.

Patch from Maneesh Soni <maneesh@in.ibm.com>

It's supposed to return an ERR_PTR value on error, not NULL.

fs/intermezzo/super.c

@@ -318,7 +318,7 @@ struct super_block * presto_get_sb(struct file_system_type *izo_type,
 
         CDEBUG(D_MALLOC, "mount error exit: kmem %ld, vmem %ld\n",
                presto_kmemory, presto_vmemory);
-        return NULL;
+        return ERR_PTR(-EINVAL);
 }