V4L/DVB (7579): bttv: Fix memory leak in radio_release

Fix the leak of the bttv_fh structure allocated in radio_open which
was introduced by commit 5cd3955c.
Signed-off-by: Robert Fitzsimons <robfitz@273k.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/bt8xx/bttv-driver.c

@@ -3463,6 +3463,9 @@ static int radio_release(struct inode *inode, struct file *file)
 	struct bttv *btv = fh->btv;
 	struct rds_command cmd;
 
+	file->private_data = NULL;
+	kfree(fh);
+
 	btv->radio_user--;
 
 	bttv_call_i2c_clients(btv, RDS_CMD_CLOSE, &cmd);