arm: dts: imx6qdl-udoo: fix rgmii phy-mode for ksz9031 phy

Commit bcf3440c6dd7 ("net: phy: micrel: add phy-mode support for the
KSZ9031 PHY") fixed micrel phy driver adding proper support for phy
modes. Adapt imx6q-udoo board phy settings : explicitly set required
delay configuration using "rgmii-id".

Fixes: cbd54fe0b2bc ("ARM: dts: imx6dl-udoo: Add board support based off imx6q-udoo")
Signed-off-by: Sergey Matyukevich <[e-mail]>
Reviewed-by: Fabio Estevam <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/boot/dts/imx6qdl-udoo.dtsi

···
 &fec {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_enet>;
-	phy-mode = "rgmii";
+	phy-mode = "rgmii-id";
 	status = "okay";
 };