dt-bindings: net: mvneta: add phys property

Add an optional phys property to the mvneta binding documentation for
the common phy.
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/marvell-armada-370-neta.txt

@@ -19,7 +19,7 @@ Optional properties:
   "marvell,armada-370-neta" and 9800B for others.
 - clock-names: List of names corresponding to clocks property; shall be
   "core" for core clock and "bus" for the optional bus clock.
-
+- phys: comphy for the ethernet port, see ../phy/phy-bindings.txt
 
 Optional properties (valid only for Armada XP/38x):