x86/xen: add missing \n at end of printk warning message

The message is missing a \n, add it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

arch/x86/xen/platform-pci-unplug.c

@@ -61,7 +61,7 @@ static int check_platform_magic(void)
 		}
 		break;
 	default:
-		printk(KERN_WARNING "Xen Platform PCI: unknown I/O protocol version");
+		printk(KERN_WARNING "Xen Platform PCI: unknown I/O protocol version\n");
 		return XEN_PLATFORM_ERR_PROTOCOL;
 	}