staging: usbip: simplified cleanup function

This patch simplified "stub_device_free" cleanup function:
 - changed return type to void, since the return value is
   not checked anywhere
 - kfree is NULL-safe, so removed if statement
 - deleted debug-message
Signed-off-by: Kurt Kanzenbach <ly80toro@cip.cs.fau.de>
Signed-off-by: Stefan Reif <ke42caxa@cip.cs.fau.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/usbip/stub_dev.c

@@ -327,15 +327,9 @@ static struct stub_device *stub_device_alloc(struct usb_device *udev,
 	return sdev;
 }
 
-static int stub_device_free(struct stub_device *sdev)
+static void stub_device_free(struct stub_device *sdev)
 {
-	if (!sdev)
-		return -EINVAL;
-
 	kfree(sdev);
-	pr_debug("kfree udev ok\n");
-
-	return 0;
 }
 
 /*