commit 
db62b9a804b4 (usb: dwc2: host: don't
use dma_alloc_coherent with irqs disabled)
introduced a build warning by using NULL
as an integer. Fix that by just using 0 instead
of NULL.
Signed-off-by: Felipe Balbi <balbi@ti.com>
 
                        chan->ep_is_in ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
        if (dma_mapping_error(hsotg->dev, qh->dw_align_buf_dma)) {
                dev_err(hsotg->dev, "can't map align_buf\n");
-               chan->align_buf = (dma_addr_t)NULL;
+               chan->align_buf = 0;
                return -EINVAL;
        }