ARM: dts: AM33xx: Add mailbox node

The mailbox DT node data has been added for AM33xx device.
The mailbox IP in AM33xx is similar to the version found in
OMAP4+ devices.
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am33xx.dtsi

@@ -347,6 +347,15 @@ dcan1: d_can@481d0000 {
 			status = "disabled";
 		};
 
+		mailbox: mailbox@480C8000 {
+			compatible = "ti,omap4-mailbox";
+			reg = <0x480C8000 0x200>;
+			interrupts = <77>;
+			ti,hwmods = "mailbox";
+			ti,mbox-num-users = <4>;
+			ti,mbox-num-fifos = <8>;
+		};
+
 		timer1: timer@44e31000 {
 			compatible = "ti,am335x-timer-1ms";
 			reg = <0x44e31000 0x400>;