s390/qeth: remove .do_ioctl() callback from driver discipline

With commit 18787eeebd ("qeth: use ndo_siocdevprivate") this callback
is now actually used to handle transport mode-specific _private_ ioctls.

We only have such ioctls for L3 devices. So wire up a L3-specific
.ndo_siocdevprivate() callback that handles those ioctls, and defers to
the core qeth_siocdevprivate() for all other private ioctls.

This takes the discipline one step closer to its original purpose of
providing an internal extension for the qeth_core_ccwgroup_driver.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_l2_main.c

@@ -2430,7 +2430,6 @@ const struct qeth_discipline qeth_l2_discipline = {
 	.remove = qeth_l2_remove_device,
 	.set_online = qeth_l2_set_online,
 	.set_offline = qeth_l2_set_offline,
-	.do_ioctl = NULL,
 	.control_event_handler = qeth_l2_control_event,
 };
 EXPORT_SYMBOL_GPL(qeth_l2_discipline);