staging: emxx_udc: Remove unneeded cast

Fix Coccinelle alert:

drivers/staging//emxx_udc/emxx_udc.c:2689:19-21: WARNING: casting value returned by memory allocation function to (u8 *) is useless.

This issue was detected by using the Coccinelle software.
Signed-off-by: Christopher Diaz Riveros <chrisadr@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/emxx_udc/emxx_udc.c

@@ -2686,7 +2686,7 @@ static int nbu2ss_ep_queue(
 
 	if (req->unaligned) {
 		if (!ep->virt_buf)
-			ep->virt_buf = (u8 *)dma_alloc_coherent(
+			ep->virt_buf = dma_alloc_coherent(
 				NULL, PAGE_SIZE,
 				&ep->phys_buf, GFP_ATOMIC | GFP_DMA);
 		if (ep->epnum > 0)  {