ARM: dts: omap3: name mdio node properly

Rename davinci_mdio DT node "ethernet"->"mdio"
This fixes the following DT schemas check errors:
am3517-craneboard.dt.yaml: ethernet@5c030000: $nodename:0: 'ethernet@5c030000' does not match '^mdio(@.*)?'
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am3517.dtsi

@@ -74,7 +74,7 @@ davinci_emac: ethernet@5c000000 {
 			clock-names = "ick";
 		};
 
-		davinci_mdio: ethernet@5c030000 {
+		davinci_mdio: mdio@5c030000 {
 			compatible = "ti,davinci_mdio";
 			ti,hwmods = "davinci_mdio";
 			status = "disabled";