ARM: dts: imx6sx-sdb: Fix the phy-mode on fec2

Commit 0672d22a1924 ("ARM: dts: imx: Fix the AR803X phy-mode") fixed the
phy-mode for fec1, but missed to fix it for the fec2 node.

Fix fec2 to also use "rgmii-id" as the phy-mode.

Cc: <[e-mail]>
Fixes: 0672d22a1924 ("ARM: dts: imx: Fix the AR803X phy-mode")
Signed-off-by: Fabio Estevam <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/boot/dts/imx6sx-sdb.dtsi

···
 &fec2 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_enet2>;
-	phy-mode = "rgmii";
+	phy-mode = "rgmii-id";
 	phy-handle = <&ethphy2>;
 	status = "okay";
 };