staging: dgnc: use dev_err() instead of printk()

Use dev_err() insted of printk() in order to provice userspace with
more useful information and use the common kernel coding style.
Signed-off-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgnc/dgnc_sysfs.c

@@ -739,7 +739,7 @@ void dgnc_create_tty_sysfs(struct un_t *un, struct device *c)
 
 	ret = sysfs_create_group(&c->kobj, &dgnc_tty_attribute_group);
 	if (ret) {
-		printk(KERN_ERR "dgnc: failed to create sysfs tty device attributes.\n");
+		dev_err(c, "dgnc: failed to create sysfs tty device attributes.\n");
 		sysfs_remove_group(&c->kobj, &dgnc_tty_attribute_group);
 		return;
 	}