net: iseries_veth: Omit check for multicast bit in netdev_for_each_mc_addr

There is no need to check for the address being a multicast address in
the netdev_for_each_mc_addr loop, so remove it.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>