dt-bindings: net: mediatek: Add support for MediaTek MT7628/88 SoC

Add compatible for the ethernet IP core on MT7628/88 SoCs. Its
compatible with the older Ralink Rt5350F SoC. And OpenWrt already
uses this compatible string for the MT76x8.
Signed-off-by: Stefan Roese <sr@denx.de>
Cc: René van Dorst <opensource@vdorst.com>
Cc: Daniel Golle <daniel@makrotopia.org>
Cc: Sean Wang <sean.wang@mediatek.com>
Cc: John Crispin <john@phrozen.org>
Cc: devicetree@vger.kernel.org
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/mediatek-net.txt

@@ -12,6 +12,7 @@ Required properties:
 		"mediatek,mt7623-eth", "mediatek,mt2701-eth": for MT7623 SoC
 		"mediatek,mt7622-eth": for MT7622 SoC
 		"mediatek,mt7629-eth": for MT7629 SoC
+		"ralink,rt5350-eth": for Ralink Rt5350F and MT7628/88 SoC
 - reg: Address and length of the register set for the device
 - interrupts: Should contain the three frame engines interrupts in numeric
 	order. These are fe_int0, fe_int1 and fe_int2.