HID: roccat: Fix NULL pointer dereference when unloading module

Class was destroyed before starting the unregistering driver chain.
Disconnecting a device from roccat chardev in this process then
raised a NULL pointer dereference.
Fixed this by destroying class after unregistering driver.

Signed-off-by: Stefan Achatz <erazor_de@users.sourceforge.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-roccat-arvo.c b/drivers/hid/hid-roccat-arvo.c
index 7b9a992..75f532f 100644
--- a/drivers/hid/hid-roccat-arvo.c
+++ b/drivers/hid/hid-roccat-arvo.c
@@ -438,8 +438,8 @@
 
 static void __exit arvo_exit(void)
 {
-	class_destroy(arvo_class);
 	hid_unregister_driver(&arvo_driver);
+	class_destroy(arvo_class);
 }
 
 module_init(arvo_init);