nfp: inherit the max_mtu from the PF netdev

The PF netdev is used for data transfer for reprs, so reprs inherit the
maximum MTU settings of the PF netdev.

Fixes: 5de73ee46704 ("nfp: general representor implementation")
Signed-off-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/nfp_net_repr.c

@@ -297,6 +297,8 @@ int nfp_repr_init(struct nfp_app *app, struct net_device *netdev,
 	netdev->netdev_ops = &nfp_repr_netdev_ops;
 	netdev->ethtool_ops = &nfp_port_ethtool_ops;
 
+	netdev->max_mtu = pf_netdev->max_mtu;
+
 	SWITCHDEV_SET_OPS(netdev, &nfp_port_switchdev_ops);
 
 	if (nfp_app_has_tc(app)) {