usb: dwc3: gadget: set request dma to invalid when unmapping

if we don't set DMA address to invalid when unmapping,
we might fall in a situation where request buffer
can't be mapped to DMA again.

Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 2ee6714..4d232c3 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -83,6 +83,7 @@
 				req->request.length, req->direction
 				? DMA_TO_DEVICE : DMA_FROM_DEVICE);
 		req->mapped = 0;
+		req->request.dma = DMA_ADDR_INVALID;
 	} else {
 		dma_sync_single_for_cpu(dwc->dev, req->request.dma,
 				req->request.length, req->direction