net: mscc: ocelot: allow unregistered IP multicast flooding to CPU

Since commit 4cf35a2b ("net: mscc: ocelot: fix broken IP multicast
flooding") from v5.12, unregistered IP multicast flooding is
configurable in the ocelot driver for bridged ports. However, by writing
0 to the PGID_MCIPV4 and PGID_MCIPV6 port masks at initialization time,
the CPU port module, for which ocelot_port_set_mcast_flood() is not
called, will have unknown IP multicast flooding disabled.

This makes it impossible for an application such as smcroute to work
properly, since all IP multicast traffic received on a standalone port
is treated as unregistered (and dropped).

Starting with commit 7569459a ("net: dsa: manage flooding on the CPU
ports"), the limitation above has been lifted, because when standalone
ports become IFF_PROMISC or IFF_ALLMULTI, ocelot_port_set_mcast_flood()
would be called on the CPU port module, so unregistered multicast is
flooded to the CPU on an as-needed basis.

But between v5.12 and v5.18, IP multicast flooding to the CPU has
remained broken, promiscuous or not.

Delete the inexplicable premature optimization of clearing PGID_MCIPV4
and PGID_MCIPV6 as part of the init sequence, and allow unregistered IP
multicast to be flooded freely to the CPU port module.

Fixes: a556c76a ("net: mscc: Add initial Ocelot switch support")
Cc: stable@kernel.org
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>