net: lapbether: use netdev_lockdep_set_classes() helper

drivers/net/wan/lapbether.c uses stacked devices.
Like similar drivers, it must use netdev_lockdep_set_classes()
to avoid LOCKDEP splats.

This is similar to commit 9bfc9d65a1dc ("hamradio:
use netdev_lockdep_set_classes() helper")

Fixes: 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations")
Reported-by: [e-mail]
Closes: https://lore.kernel.org/lkml/[e-mail]/T/#u
Signed-off-by: Eric Dumazet <[e-mail]>
Acked-by: Stanislav Fomichev <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/wan/lapbether.c

···
 #include <linux/lapb.h>
 #include <linux/init.h>
 
+#include <net/netdev_lock.h>
 #include <net/x25device.h>
 
 static const u8 bcast_addr[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
···
 
 static void lapbeth_setup(struct net_device *dev)
 {
+	netdev_lockdep_set_classes(dev);
 	dev->netdev_ops	     = &lapbeth_netdev_ops;
 	dev->needs_free_netdev = true;
 	dev->type            = ARPHRD_X25;