Fix the following checkpatch warning:
WARNING: Prefer [subsystem eg: netdev]_err([subsystem]dev, ...
then dev_err(dev, ... then pr_err(...  to printk(KERN_ERR ...
Signed-off-by: Ioana Ciornei <ciorneiioana@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
        rc |= driver_create_file(driverfs, &driver_attr_maxboards);
        rc |= driver_create_file(driverfs, &driver_attr_pollrate);
        if (rc)
-               printk(KERN_ERR "DGNC: sysfs driver_create_file failed!\n");
+               pr_err("DGNC: sysfs driver_create_file failed!\n");
 }