The devm_ioremap() function doesn't return error pointers, it returns
NULL.  Update the error checking to match.
Fixes: 5d4d263e1c6b ("mailbox: Introduce support for T-head TH1520 Mailbox driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Michal Wilczynski <m.wilczynski@samsung.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>
 
        mapped = devm_ioremap(&pdev->dev, res->start + offset,
                              resource_size(res) - offset);
-       if (IS_ERR(mapped))
+       if (!mapped) {
                dev_err(&pdev->dev, "Failed to map resource: %s\n", res_name);
+               return ERR_PTR(-ENOMEM);
+       }
 
        return mapped;
 }