ARM: dts: am572x-idk: Enable the system mailboxes 5 and 6

Enable the System Mailboxes 5 and 6 and the corresponding
child sub-mailbox (IPC 3.x) nodes for the AM572x IDK board.
This is needed to enable communication with the respective
remote processors IPU1, IPU2, DSP1 and DSP2 from the MPU.
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am572x-idk.dts

@@ -91,3 +91,23 @@ &sn65hvs882 {
 &pcie1 {
 	gpios = <&gpio3 23 GPIO_ACTIVE_HIGH>;
 };
+
+&mailbox5 {
+	status = "okay";
+	mbox_ipu1_ipc3x: mbox_ipu1_ipc3x {
+		status = "okay";
+	};
+	mbox_dsp1_ipc3x: mbox_dsp1_ipc3x {
+		status = "okay";
+	};
+};
+
+&mailbox6 {
+	status = "okay";
+	mbox_ipu2_ipc3x: mbox_ipu2_ipc3x {
+		status = "okay";
+	};
+	mbox_dsp2_ipc3x: mbox_dsp2_ipc3x {
+		status = "okay";
+	};
+};