dt-bindings: net: dsa: realtek: convert to YAML schema, add MDIO

Schema changes:

- support for mdio-connected switches (mdio driver), recognized by
  checking the presence of property "reg"
- new compatible strings for rtl8367s and rtl8367rb
- "interrupt-controller" was not added as a required property. It might
  still work polling the ports when missing.

Examples changes:

- renamed "switch_intc" to make it unique between examples
- removed "dsa-mdio" from mdio compatible property
- renamed phy@0 to ethernet-phy@0 (not tested with real HW)
  phy@ requires #phy-cells

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>