drivers/watchdog/lantiq_wdt.c: drop iounmap for devm_ allocated data

Data allocated with devm_ioremap or devm_ioremap_nocache should not be
freed using iounmap, because doing so causes a dangling pointer, and a
subsequent double free.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@r@
expression x;
@@
(
 x = devm_ioremap(...)
|
 x = devm_ioremap_nocache(...)
)

@@
expression r.x;
@@
* iounmap(x)
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/lantiq_wdt.c

@@ -222,9 +222,6 @@ ltq_wdt_remove(struct platform_device *pdev)
 {
 	misc_deregister(&ltq_wdt_miscdev);
 
-	if (ltq_wdt_membase)
-		iounmap(ltq_wdt_membase);
-
 	return 0;
 }