ASoC: zx: spdif: Fix devm_ioremap_resource return value check

Value returned by devm_ioremap_resource() was checked for non-NULL but
devm_ioremap_resource() returns IOMEM_ERR_PTR, not NULL. In case of
error this could lead to dereference of ERR_PTR.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Reviewed-by: Jun Nie <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/zte/zx296702-spdif.c

···
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	zx_spdif->mapbase = res->start;
 	zx_spdif->reg_base = devm_ioremap_resource(&pdev->dev, res);
-	if (!zx_spdif->reg_base) {
+	if (IS_ERR(zx_spdif->reg_base)) {
 		dev_err(&pdev->dev, "ioremap failed!\n");
-		return -EIO;
+		return PTR_ERR(zx_spdif->reg_base);
 	}
 
 	zx_spdif_dev_init(zx_spdif->reg_base);