usb: musb: honour the return value of dma_map_single()

Since dma_map_single() may fail it is good to actually check the return
code to see if it succeeded.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_gadget.c

@@ -76,13 +76,21 @@ static inline void map_dma_buffer(struct musb_request *request,
 		return;
 
 	if (request->request.dma == DMA_ADDR_INVALID) {
-		request->request.dma = dma_map_single(
+		dma_addr_t dma_addr;
+		int ret;
+
+		dma_addr = dma_map_single(
 				musb->controller,
 				request->request.buf,
 				request->request.length,
 				request->tx
 					? DMA_TO_DEVICE
 					: DMA_FROM_DEVICE);
+		ret = dma_mapping_error(musb->controller, dma_addr);
+		if (ret)
+			return;
+
+		request->request.dma = dma_addr;
 		request->map_state = MUSB_MAPPED;
 	} else {
 		dma_sync_single_for_device(musb->controller,