drm/tegra: nvdec: Fix dma_alloc_coherent error check

Check for NULL return value with dma_alloc_coherent, in line with
Robin's fix for vic.c in 'drm/tegra: vic: Fix DMA API misuse'.

Fixes: 46f226c93d35 ("drm/tegra: Add NVDEC driver")
Signed-off-by: Mikko Perttunen <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/tegra/nvdec.c

···
 
 	if (!client->group) {
 		virt = dma_alloc_coherent(nvdec->dev, size, &iova, GFP_KERNEL);
-
-		err = dma_mapping_error(nvdec->dev, iova);
-		if (err < 0)
-			return err;
+		if (!virt)
+			return -ENOMEM;
 	} else {
 		virt = tegra_drm_alloc(tegra, size, &iova);
 		if (IS_ERR(virt))