usb: gadget: Clear usb_endpoint_descriptor inside the struct usb_ep on disable

This fix a bug in f_serial, which expect the ep->desc to be NULL after
disabling an endpoint.

Cc: stable@vger.kernel.org
Signed-off-by: Ido Shayevitz <idos@codeaurora.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/gadget/s3c-hsudc.c b/drivers/usb/gadget/s3c-hsudc.c
index 5e87293..ace95f9 100644
--- a/drivers/usb/gadget/s3c-hsudc.c
+++ b/drivers/usb/gadget/s3c-hsudc.c
@@ -817,6 +817,7 @@
 	s3c_hsudc_nuke_ep(hsep, -ESHUTDOWN);
 
 	hsep->desc = 0;
+	hsep->ep.desc = NULL;
 	hsep->stopped = 1;
 
 	spin_unlock_irqrestore(&hsudc->lock, flags);
@@ -1006,6 +1007,7 @@
 	hsep->ep.ops = &s3c_hsudc_ep_ops;
 	hsep->fifo = hsudc->regs + S3C_BR(epnum);
 	hsep->desc = 0;
+	hsep->ep.desc = NULL;
 	hsep->stopped = 0;
 	hsep->wedge = 0;