staging: emxx_udc: Fix passing of NULL to dma_alloc_coherent()

In nbu2ss_eq_queue() memory is allocated with dma_alloc_coherent(),
though, strangely, NULL is passed as the struct device* argument. Pass
the UDC's device instead. Fix up the corresponding call to
dma_free_coherent() in the same way.

Build-tested on x86 only.

Fixes: 33aa8d45 ("staging: emxx_udc: Add Emma Mobile USB Gadget driver")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Link: https://lore.kernel.org/r/20200825091928.55794-1-alex.dewar90@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/emxx_udc/emxx_udc.c

@@ -2593,7 +2593,7 @@ static int nbu2ss_ep_queue(struct usb_ep *_ep,
 
 	if (req->unaligned) {
 		if (!ep->virt_buf)
-			ep->virt_buf = dma_alloc_coherent(NULL, PAGE_SIZE,
+			ep->virt_buf = dma_alloc_coherent(udc->dev, PAGE_SIZE,
 							  &ep->phys_buf,
 							  GFP_ATOMIC | GFP_DMA);
 		if (ep->epnum > 0)  {
@@ -3148,7 +3148,7 @@ static int nbu2ss_drv_remove(struct platform_device *pdev)
 	for (i = 0; i < NUM_ENDPOINTS; i++) {
 		ep = &udc->ep[i];
 		if (ep->virt_buf)
-			dma_free_coherent(NULL, PAGE_SIZE, (void *)ep->virt_buf,
+			dma_free_coherent(udc->dev, PAGE_SIZE, (void *)ep->virt_buf,
 					  ep->phys_buf);
 	}