can: make use of preallocated can_ml_priv for per device struct can_dev_rcv_lists

This patch removes the old method of allocating the per device protocol
specific memory via a netdevice_notifier. This had the drawback, that
the allocation can fail, leading to a lot of null pointer checks in the
code. This also makes the live cycle management of this memory quite
complicated.

This patch switches from the allocating the struct can_dev_rcv_lists in
a NETDEV_REGISTER call to using the dev->ml_priv, which is allocated by
the driver since the previous patch.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/slcan.c

@@ -536,6 +536,7 @@ static struct slcan *slc_alloc(void)
 
 	dev->base_addr  = i;
 	sl = netdev_priv(dev);
+	dev->ml_priv = (void *)sl + ALIGN(sizeof(*sl), NETDEV_ALIGN);
 
 	/* Initialize channel control data */
 	sl->magic = SLCAN_MAGIC;