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

Always unmap all SG entries as required by DMA API

Fixes: a698908d3b3b ("usb: gadget: add generic map/unmap request utilities")
Cc: <stable@vger.kernel.org> # v3.4+
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/udc/core.c

@@ -827,7 +827,7 @@ void usb_gadget_unmap_request_by_dev(struct device *dev,
 		return;
 
 	if (req->num_mapped_sgs) {
-		dma_unmap_sg(dev, req->sg, req->num_mapped_sgs,
+		dma_unmap_sg(dev, req->sg, req->num_sgs,
 				is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
 
 		req->num_mapped_sgs = 0;