xenbus: don't free other end details too early

The individual drivers' remove functions could legitimately attempt to
access this information (for logging messages if nothing else). Note
that I did not in fact observe a problem anywhere, but I came across
this while looking into the reasons for what turned out to need the
fix at https://lkml.org/lkml/2012/3/5/336 to vsprintf().
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/xenbus/xenbus_probe.c

@@ -257,11 +257,12 @@ int xenbus_dev_remove(struct device *_dev)
 	DPRINTK("%s", dev->nodename);
 
 	free_otherend_watch(dev);
-	free_otherend_details(dev);
 
 	if (drv->remove)
 		drv->remove(dev);
 
+	free_otherend_details(dev);
+
 	xenbus_switch_state(dev, XenbusStateClosed);
 	return 0;
 }