board: sl28: add DSA support for variant 2

Now that u-boot gained DSA support, and it is already enabled for the
kontron_sl28 board, add the last missing piece and enable the
corresponding devices it in the device tree.

Signed-off-by: Michael Walle <michael@walle.cc>
diff --git a/arch/arm/dts/fsl-ls1028a-kontron-sl28-var2-u-boot.dtsi b/arch/arm/dts/fsl-ls1028a-kontron-sl28-var2-u-boot.dtsi
index 79b771e..4e0ce3f 100644
--- a/arch/arm/dts/fsl-ls1028a-kontron-sl28-var2-u-boot.dtsi
+++ b/arch/arm/dts/fsl-ls1028a-kontron-sl28-var2-u-boot.dtsi
@@ -1,2 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0+
 #include "fsl-ls1028a-kontron-sl28-u-boot.dtsi"
+
+/ {
+	aliases {
+		ethernet0 = &mscc_felix_port0;
+		ethernet1 = &mscc_felix_port1;
+	};
+};