usb: musb: gadget: prevent a NULL pointer dereference

Case we can't allocate struct musb_request,
prevent a NULL pointer dereference by returning
early.

Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_gadget.c

@@ -1072,13 +1072,16 @@ struct usb_request *musb_alloc_request(struct usb_ep *ep, gfp_t gfp_flags)
 	struct musb_request	*request = NULL;
 
 	request = kzalloc(sizeof *request, gfp_flags);
-	if (request) {
-		INIT_LIST_HEAD(&request->request.list);
-		request->request.dma = DMA_ADDR_INVALID;
-		request->epnum = musb_ep->current_epnum;
-		request->ep = musb_ep;
+	if (!request) {
+		DBG(4, "not enough memory\n");
+		return NULL;
 	}
 
+	INIT_LIST_HEAD(&request->request.list);
+	request->request.dma = DMA_ADDR_INVALID;
+	request->epnum = musb_ep->current_epnum;
+	request->ep = musb_ep;
+
 	return &request->request;
 }