dt-bindings: net: snps: remove duplicate name

snps,dwmac has duplicated name for loongson,ls2k-dwmac and
loongson,ls7a-dwmac.
Signed-off-by: Dongjin Yang <dj76.yang@samsung.com>
Fixes: 68277749 ("dt-bindings: dwmac: Add bindings for new Loongson SoC and bridge chip")
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220404022857epcms1p6e6af1a6a86569f339e50c318abde7d3c@epcms1p6

Documentation/devicetree/bindings/net/snps,dwmac.yaml

@@ -53,20 +53,18 @@ properties:
         - allwinner,sun8i-r40-gmac
         - allwinner,sun8i-v3s-emac
         - allwinner,sun50i-a64-emac
-        - loongson,ls2k-dwmac
-        - loongson,ls7a-dwmac
         - amlogic,meson6-dwmac
         - amlogic,meson8b-dwmac
         - amlogic,meson8m2-dwmac
         - amlogic,meson-gxbb-dwmac
         - amlogic,meson-axg-dwmac
-        - loongson,ls2k-dwmac
-        - loongson,ls7a-dwmac
         - ingenic,jz4775-mac
         - ingenic,x1000-mac
         - ingenic,x1600-mac
         - ingenic,x1830-mac
         - ingenic,x2000-mac
+        - loongson,ls2k-dwmac
+        - loongson,ls7a-dwmac
         - rockchip,px30-gmac
         - rockchip,rk3128-gmac
         - rockchip,rk3228-gmac