CVE-2026-43103 net: lapbether: handle NETDEV_PRE_TYPE_CHANGE

In the Linux kernel, the following vulnerability has been resolved: net: lapbether: handle NETDEVPRETYPECHANGE lapbethdatatransmit expects the underlying device type to be ARPHRDETHER. Returning NOTIFYBAD from lapbethdeviceevent makes sure bonding driver can not break this expectation...