HID: hid-belkin: clean up usage of 'driver_data'

The module is storing an integer inside the drvdata pointer, which is
confusing, lets fix this and set the whole of 'hid_device_id' struct
as the drvdata and then simply use its integer 'driver_data' field for
quirks, which shall make the code cleaner, type-safe, consistent and
more readable.

This makes the cast to (void *) during storage a bit safer (just to
suppress the const qualifier warning) and the cast to (unsigned long)
during retrieval is removed.

Signed-off-by: Pawel Zalewski (The Capable Hub) <pzalewski@thegoodpenguin.co.uk>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

Author: pzalewski-thegoodpenguin

drivers/hid/hid-belkin.c

@@ -27,7 +27,8 @@ static int belkin_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 		struct hid_field *field, struct hid_usage *usage,
 		unsigned long **bit, int *max)
 {
-	unsigned long quirks = (unsigned long)hid_get_drvdata(hdev);
+	const struct hid_device_id *id = hid_get_drvdata(hdev);
+	unsigned long quirks = id->driver_data;
 
 	if ((usage->hid & HID_USAGE_PAGE) != HID_UP_CONSUMER ||
 			!(quirks & BELKIN_WKBD))
@@ -48,7 +49,7 @@ static int belkin_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	unsigned long quirks = id->driver_data;
 	int ret;
 
-	hid_set_drvdata(hdev, (void *)quirks);
+	hid_set_drvdata(hdev, (void *)id);
 
 	ret = hid_parse(hdev);
 	if (ret) {