USB: roles: make role_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the role_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at load time.

Suggested-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Ivan Orlov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/roles/class.c

···
 #include <linux/mutex.h>
 #include <linux/slab.h>
 
-static struct class *role_class;
+static const struct class role_class = {
+	.name = "usb_role",
+};
 
 struct usb_role_switch {
 	struct device dev;
···
 	if (id && !fwnode_property_present(fwnode, id))
 		return NULL;
 
-	dev = class_find_device_by_fwnode(role_class, fwnode);
+	dev = class_find_device_by_fwnode(&role_class, fwnode);
 
 	return dev ? to_role_switch(dev) : ERR_PTR(-EPROBE_DEFER);
 }
···
 		return NULL;
 	}
 
-	dev = class_find_device_by_fwnode(role_class, parent);
+	dev = class_find_device_by_fwnode(&role_class, parent);
 	fwnode_handle_put(parent);
 	return dev ? to_role_switch(dev) : ERR_PTR(-EPROBE_DEFER);
 }
···
 	if (!fwnode)
 		return NULL;
 
-	dev = class_find_device_by_fwnode(role_class, fwnode);
+	dev = class_find_device_by_fwnode(&role_class, fwnode);
 	if (dev)
 		WARN_ON(!try_module_get(dev->parent->driver->owner));
 
···
 
 	sw->dev.parent = parent;
 	sw->dev.fwnode = desc->fwnode;
-	sw->dev.class = role_class;
+	sw->dev.class = &role_class;
 	sw->dev.type = &usb_role_dev_type;
 	dev_set_drvdata(&sw->dev, desc->driver_data);
 	dev_set_name(&sw->dev, "%s-role-switch",
···
 
 static int __init usb_roles_init(void)
 {
-	role_class = class_create("usb_role");
-	return PTR_ERR_OR_ZERO(role_class);
+	return class_register(&role_class);
 }
 subsys_initcall(usb_roles_init);
 
 static void __exit usb_roles_exit(void)
 {
-	class_destroy(role_class);
+	class_unregister(&role_class);
 }
 module_exit(usb_roles_exit);