mtd: denali_dt: Fix incorrect error check

The return value of devm_ioremap_nocache should be checked here instead
of res.
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/denali_dt.c

@@ -42,7 +42,7 @@ static void __iomem *request_and_map(struct device *dev,
 	}
 
 	ptr = devm_ioremap_nocache(dev, res->start, resource_size(res));
-	if (!res)
+	if (!ptr)
 		dev_err(dev, "ioremap_nocache of %s failed!", res->name);
 
 	return ptr;