WMI: properly cleanup devices to avoid crashes

We need to remove devices that we destroy from the list, otherwise
we'll crash if there are more than one "_WDG" methods in DSDT.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=32052

Tested-by: Ilya Tumaykin <librarian_rus@yahoo.com>
Cc: stable@kernel.org
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Acked-by: Carlos Corbacho <carlos@strangeworlds.co.uk>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/wmi.c

@@ -754,9 +754,13 @@ static void wmi_free_devices(void)
 	struct wmi_block *wblock, *next;
 
 	/* Delete devices for all the GUIDs */
-	list_for_each_entry_safe(wblock, next, &wmi_block_list, list)
+	list_for_each_entry_safe(wblock, next, &wmi_block_list, list) {
+		list_del(&wblock->list);
 		if (wblock->dev.class)
 			device_unregister(&wblock->dev);
+		else
+			kfree(wblock);
+	}
 }
 
 static bool guid_already_parsed(const char *guid_string)