ARM: dts: BCM5301X: Explicitly disable unused switch CPU ports

ARM: dts: BCM5301X: Explicitly disable unused switch CPU ports

[ Upstream commit 473baeab929444295b0530f8766e4becb6a08973 ]

When redescribing ports I assumed that missing "label" (like "cpu")
means switch port isn't used. That was incorrect and I realized my
change made Linux always use the first (5) CPU port (there are 3 of
them).

While above should technically be possible it often isn't correct:
1. Non-default switch ports are often connected to Ethernet interfaces
   not fully covered by vendor setup (they may miss MACs)
2. On some devices non-default ports require specifying fixed link

This fixes network connectivity for some devices. It was reported &
tested for Netgear R8000. It also affects Linksys EA9200 with its
downstream DTS.

Fixes: ba4aebce23b2 ("ARM: dts: BCM5301X: Describe switch ports in the main DTS")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Link: https://lore.kernel.org/r/20231013103314.10306-1-zajec5@gmail.com
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>