realtek: dts: relocate/retype switch node

realtek: dts: relocate/retype switch node

The switch node is currently located outside of the switchcore@1b000000
tree. This makes it hard to find when referencing from other nodes in
this tree. Make it a subnode of switchcore and "retype" it to
ethernet-switch like upstream does.

This is not perfectly aligned as upstream just mixes the switchcore and
the ethernet-switch node into one. But this will be future work for
downstream.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/22236
Signed-off-by: Robert Marko <robert.marko@sartura.hr>