staging: usbip: remove redundant return statements

Remove redundant return statements at the end of void functions. This
addresses the checkpatch.pl warnings:

	WARNING: void function return statements are not generally useful

Signed-off-by: Max Vozeler <max@hinterhof.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/usbip/stub_rx.c

@@ -529,7 +529,6 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 	}
 
 	usbip_dbg_stub_rx("Leave\n");
-	return;
 }
 
 /* recv a pdu */

drivers/staging/usbip/vhci_hcd.c

@@ -1121,7 +1121,6 @@ static struct platform_driver vhci_driver = {
  */
 static void the_pdev_release(struct device *dev)
 {
-	return;
 }
 
 static struct platform_device the_pdev = {

drivers/staging/usbip/vhci_rx.c

@@ -111,8 +111,6 @@ static void vhci_recv_ret_submit(struct vhci_device *vdev,
 	usb_hcd_giveback_urb(vhci_to_hcd(the_controller), urb, urb->status);
 
 	usbip_dbg_vhci_rx("Leave\n");
-
-	return;
 }
 
 static struct vhci_unlink *dequeue_pending_unlink(struct vhci_device *vdev,