dt-bindings: net: meson-dwmac: new compatible name for AXG SoC

We need to introduce a new compatible name for the Meson-AXG SoC
in order to support the RMII 100M ethernet PHY, since the PRG_ETH0
register of the dwmac glue layer is changed from previous old SoC.
Signed-off-by: Yixun Lan <yixun.lan@amlogic.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/meson-dwmac.txt

@@ -11,6 +11,7 @@ Required properties on all platforms:
 			- "amlogic,meson8b-dwmac"
 			- "amlogic,meson8m2-dwmac"
 			- "amlogic,meson-gxbb-dwmac"
+			- "amlogic,meson-axg-dwmac"
 		Additionally "snps,dwmac" and any applicable more
 		detailed version number described in net/stmmac.txt
 		should be used.