net: dsa: b53: Fix egress flooding settings

There were several issues with 53568438 ("net: dsa: b53: Add support for port_egress_floods callback") that resulted in breaking connectivity for standalone ports:

- both user and CPU ports must allow unicast and multicast forwarding by
  default otherwise this just flat out breaks connectivity for
  standalone DSA ports
- IP multicast is treated similarly as multicast, but has separate
  control registers
- the UC, MC and IPMC lookup failure register offsets were wrong, and
  instead used bit values that are meaningful for the
  B53_IP_MULTICAST_CTRL register

Fixes: 53568438 ("net: dsa: b53: Add support for port_egress_floods callback")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>