usb: gadget: udc: core: don't starve DMA resources

commit 23fd537c upstream.

Always unmap all SG entries as required by DMA API

Fixes: a698908d ("usb: gadget: add generic map/unmap request utilities")
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
[bwh: Backported to 3.16: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/gadget/udc-core.c

@@ -91,7 +91,7 @@ void usb_gadget_unmap_request(struct usb_gadget *gadget,
 		return;
 
 	if (req->num_mapped_sgs) {
-		dma_unmap_sg(&gadget->dev, req->sg, req->num_mapped_sgs,
+		dma_unmap_sg(&gadget->dev, req->sg, req->num_sgs,
 				is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
 
 		req->num_mapped_sgs = 0;