USB: legousbtower: fix memleak on disconnect

If disconnect() races with release() after a process has been
interrupted, release() could end up returning early and the driver would
fail to free its driver data.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191010125835.27031-3-johan@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/legousbtower.c

@@ -419,10 +419,7 @@ static int tower_release (struct inode *inode, struct file *file)
 		goto exit;
 	}
 
-	if (mutex_lock_interruptible(&dev->lock)) {
-	        retval = -ERESTARTSYS;
-		goto exit;
-	}
+	mutex_lock(&dev->lock);
 
 	if (dev->open_count != 1) {
 		dev_dbg(&dev->udev->dev, "%s: device not opened exactly once\n",