mlxsw: spectrum: Enable macvlan upper devices

In order to allow more unicast MAC addresses (e.g., VRRP virtual MAC) to
be directed to the router we need to enable macvlan uppers on top of
mlxsw netdevs.

Allow macvlan upper devices on top of mlxsw netdevs and sanitize
configurations that can't work. For example, a macvlan can't be enslaved
to a bridge as without ACLs the device doesn't take the destination MAC
into account when classifying a packet to a bridge instance (i.e., a
FID).

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>