powerpc: Enable device tree support for P2041RDB

Add device tree for P1041RDB board and enable CONFIG_OF_CONTROL
so that device tree can be compiled.
Update board README for device tree usage.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/arch/powerpc/dts/p2041rdb.dts b/arch/powerpc/dts/p2041rdb.dts
new file mode 100644
index 0000000..6e9d9c0
--- /dev/null
+++ b/arch/powerpc/dts/p2041rdb.dts
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0+ OR X11
+/*
+ * P2041RDB Device Tree Source
+ *
+ * Copyright 2011 - 2015 Freescale Semiconductor Inc.
+ * Copyright 2019 NXP
+ */
+
+/include/ "p2041.dtsi"
+
+/ {
+	model = "fsl,P2041RDB";
+	compatible = "fsl,P2041RDB";
+	#address-cells = <2>;
+	#size-cells = <2>;
+	interrupt-parent = <&mpic>;
+
+};