ARM: dts: BCM5301X: Describe switch ports in the main DTS

ARM: dts: BCM5301X: Describe switch ports in the main DTS

All Northstar SoCs have BCM5301x switches (BCM53011, BCM53012) with 8
ports (0-8 without 6). By design 3 switch ports (5, 7 and 8) are
hardwired to 3 on-SoC Ethernet interfaces. Switch port 8 requires
forcing link state.

It seems that global Northstar .dtsi file is the best place to describe
those hw details. Only device specific bits (like labels) should go to
device .dts files.

This seems to fit well with a tiny exception of Asus RT-AC88U which
somehow was designed to have switch 5 connected to an extra switch. This
case was simply handled with a /delete-property/.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Christian Lamparter <chunkeey@gmail.com> (MR32+MR26)
Link: https://lore.kernel.org/r/20230605132109.7933-1-zajec5@gmail.com
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>