HID: thrustmaster: fix sparse warnings

Changed 0 to NULL to fix following sparse warnings:

    drivers/hid/hid-thrustmaster.c:208:43: warning: Using plain integer as NULL pointer
    drivers/hid/hid-thrustmaster.c:241:17: warning: Using plain integer as NULL pointer
    drivers/hid/hid-thrustmaster.c:275:37: warning: Using plain integer as NULL pointer
Signed-off-by: Vihas Mak <makvihas@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-thrustmaster.c

@@ -205,7 +205,7 @@ static void thrustmaster_model_handler(struct urb *urb)
 	struct tm_wheel *tm_wheel = hid_get_drvdata(hdev);
 	uint16_t model = 0;
 	int i, ret;
-	const struct tm_wheel_info *twi = 0;
+	const struct tm_wheel_info *twi = NULL;
 
 	if (urb->status) {
 		hid_err(hdev, "URB to get model id failed with error %d\n", urb->status);
@@ -238,7 +238,7 @@ static void thrustmaster_model_handler(struct urb *urb)
 		tm_wheel->usb_dev,
 		usb_sndctrlpipe(tm_wheel->usb_dev, 0),
 		(char *)tm_wheel->change_request,
-		0, 0, // We do not expect any response from the wheel
+		NULL, 0, // We do not expect any response from the wheel
 		thrustmaster_change_handler,
 		hdev
 	);
@@ -272,7 +272,7 @@ static void thrustmaster_remove(struct hid_device *hdev)
 static int thrustmaster_probe(struct hid_device *hdev, const struct hid_device_id *id)
 {
 	int ret = 0;
-	struct tm_wheel *tm_wheel = 0;
+	struct tm_wheel *tm_wheel = NULL;
 
 	ret = hid_parse(hdev);
 	if (ret) {