net: dsa: felix: restore multicast flood to CPU when NPI tagger reinitializes

ocelot_init sets up PGID_MC to include the CPU port module, and that is
fine, but the ocelot-8021q tagger removes the CPU port module from the
unknown multicast replicator. So after a transition from the default
ocelot tagger towards ocelot-8021q and then again towards ocelot,
multicast flooding towards the CPU port module will be disabled.

Fixes: e21268ef

 ("net: dsa: felix: perform switch setup for tag_8021q")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>