usb: roles: add lockdep class key to struct usb_role_switch

There can be multiple role switch devices running on a platform. Given
that lockdep is not capable of differentiating between locks of
different instances, false positive warnings for circular locking are
reported. To prevent this, register unique lockdep key for each of the
individual instances.

Signed-off-by: Amit Sunil Dhamne <[e-mail]>
Reviewed-by: Badhri Jagan Sridharan <[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/usb/role.h>
 #include <linux/property.h>
 #include <linux/device.h>
+#include <linux/lockdep.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
···
 	usb_role_switch_set_t set;
 	usb_role_switch_get_t get;
 	bool allow_userspace_control;
+
+	struct lock_class_key key;
 };
 
 #define to_role_switch(d)	container_of(d, struct usb_role_switch, dev)
···
 
 	sw->registered = true;
 
+	lockdep_register_key(&sw->key);
+	lockdep_set_class(&sw->lock, &sw->key);
+
 	/* TODO: Symlinks for the host port and the device controller. */
 
 	return sw;
···
 {
 	if (IS_ERR_OR_NULL(sw))
 		return;
+
+	lockdep_unregister_key(&sw->key);
+
 	sw->registered = false;
 	if (dev_fwnode(&sw->dev))
 		component_del(&sw->dev, &connector_ops);