ARM: dts: BCM5301X: Set fixed-link for extra Netgear R8000 CPU ports

ARM: dts: BCM5301X: Set fixed-link for extra Netgear R8000 CPU ports

Ports 5 and 7 are disabled by default because the standard use case is
for port 8 to manage all CPU directed traffic. For experimentation
purposes however it is desirable to provide adequate properties such
that people can experiment with using different ports without having to
figure out their configuration. Some of the use cases include but are
not limited to doubling or tripling the bandwidth by leveraging the
additional ports/Ethernet MAC combinations.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Link: https://lore.kernel.org/r/20231013103314.10306-2-zajec5@gmail.com
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>