dt-bindings: net: litex,liteeth: Correct example indentation

DTS example in the bindings should be indented with 2- or 4-spaces, so
correct a mixture of different styles to keep consistent 4-spaces.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Gabriel Somlo <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

Documentation/devicetree/bindings/net/litex,liteeth.yaml

···
         phy-handle = <&eth_phy>;
 
         mdio {
-          #address-cells = <1>;
-          #size-cells = <0>;
+            #address-cells = <1>;
+            #size-cells = <0>;
 
-          eth_phy: ethernet-phy@0 {
-            reg = <0>;
-          };
+            eth_phy: ethernet-phy@0 {
+                reg = <0>;
+            };
         };
     };
 ...