dt-bindings: net: Document moca PHY interface

MoCA (Multimedia over Coaxial) is used by the internal GENET/MOCA cores
and will be needed in order to convert GENET to YAML in subsequent
changes.

Signed-off-by: Florian Fainelli <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/net/ethernet-controller.yaml

···
       - rev-mii
       - rmii
       - rev-rmii
+      - moca
 
       # RX and TX delays are added by the MAC when required
       - rgmii