ipvlan: use ETH_MAX_MTU as max mtu

Similar to the fixes on team and bonding, this restores the ability
to set an ipvlan device's mtu to anything higher than 1500.

Fixes: 91572088 ("net: use core MTU range checking in core net infra")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>