ieee802154: add helper wpan_phy_to_rdev function

This patch introduce a function to get the cfg802154_registered_device
from a wpan_phy.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/ieee802154/core.h

@@ -12,6 +12,14 @@ struct cfg802154_registered_device {
 	struct wpan_phy wpan_phy __aligned(NETDEV_ALIGN);
 };
 
+static inline struct cfg802154_registered_device *
+wpan_phy_to_rdev(struct wpan_phy *wpan_phy)
+{
+	BUG_ON(!wpan_phy);
+	return container_of(wpan_phy, struct cfg802154_registered_device,
+			    wpan_phy);
+}
+
 /* free object */
 void cfg802154_dev_free(struct cfg802154_registered_device *rdev);