HID: fix memleaking of collection

hid_free_device() doesn't free device->collection (but it does
free device->rdesc and device itself). This imposes memory leak.
Fix it.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-core.c

@@ -543,6 +543,7 @@ void hid_free_device(struct hid_device *device)
 	}
 
 	kfree(device->rdesc);
+	kfree(device->collection);
 	kfree(device);
 }
 EXPORT_SYMBOL_GPL(hid_free_device);