dmaengine: nbpfaxi: Add missing check after DMA map

The DMA map functions can fail and should be tested for errors.
If the mapping fails, unmap and return an error.

Fixes: b45b262cefd5 ("dmaengine: add a driver for AMBA AXI NBPF DMAC IP cores")
Signed-off-by: Thomas Fourier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/nbpfaxi.c

···
 		list_add_tail(&ldesc->node, &lhead);
 		ldesc->hwdesc_dma_addr = dma_map_single(dchan->device->dev,
 					hwdesc, sizeof(*hwdesc), DMA_TO_DEVICE);
+		if (dma_mapping_error(dchan->device->dev,
+				      ldesc->hwdesc_dma_addr))
+			goto unmap_error;
 
 		dev_dbg(dev, "%s(): mapped 0x%p to %pad\n", __func__,
 			hwdesc, &ldesc->hwdesc_dma_addr);
···
 	spin_unlock_irq(&chan->lock);
 
 	return ARRAY_SIZE(dpage->desc);
+
+unmap_error:
+	while (i--) {
+		ldesc--; hwdesc--;
+
+		dma_unmap_single(dchan->device->dev, ldesc->hwdesc_dma_addr,
+				 sizeof(hwdesc), DMA_TO_DEVICE);
+	}
+
+	return -ENOMEM;
 }
 
 static void nbpf_desc_put(struct nbpf_desc *desc)