arm: dts: ls1028a-rdb: enable PCIe controllers from U-Boot dtsi

Reuse the scheme implemented by the Kontron SL28 boards in
commit d08011d7f9
("arm: dts: ls1028a: disable the PCIe controller by default")
and move the 'status = "okay"' lines for the PCIe controllers
inside a separate U-Boot dtsi for the LS1028A-RDB board. This way, the
existing Linux device tree can simply be dropped in.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>

arch/arm/dts/fsl-ls1028a-rdb-u-boot.dtsi

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright 2021 NXP */
+
+/*
+ * u-boot will enable the device in the linux device tree in place. Because
+ * we are using the linux device tree, we have to enable the PCI controller
+ * ourselves.
+ */
+&pcie1 {
+	status = "okay";
+};
+
+&pcie2 {
+	status = "okay";
+};

arch/arm/dts/fsl-ls1028a-rdb.dts

@@ -153,14 +153,6 @@
 	status = "okay";
 };
 
-&pcie1 {
-	status = "okay";
-};
-
-&pcie2 {
-	status = "okay";
-};
-
 &sata {
 	status = "okay";
 };