arm64: dts: ti: k3-am64*: Disable ethernet by default at SoC level

arm64: dts: ti: k3-am64*: Disable ethernet by default at SoC level

External interfaces should be disabled at the SoC DTSI level, since
the node is incomplete. Disable Ethernet switch and ports in SoC DTSI
and enable them in the board DTS. If the board DTS includes a SoM DTSI
that completes the node description, enable the Ethernet switch and
ports in SoM DTSI.

Reflect this change in SoM DTSIs by removing ethernet port disable.

Signed-off-by: Logan Bristol <logan.bristol@utexas.edu>
Acked-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Acked-by: Josua Mayer <josua@solid-run.com>
Link: https://lore.kernel.org/r/20240809135753.1186-1-logan.bristol@utexas.edu
Signed-off-by: Nishanth Menon <nm@ti.com>