ARM: dts: am437x-sk: add power button binding

Let this board report KEY_POWER so upper layers
can decide what to do when power button is pressed.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am437x-sk-evm.dts

@@ -444,6 +444,11 @@ ldo1: regulator-ldo1 {
 			regulator-always-on;
 		};
 
+		power-button {
+			compatible = "ti,tps65218-pwrbutton";
+			status = "okay";
+			interrupts = <3 IRQ_TYPE_EDGE_BOTH>;
+		};
 	};
 
 	at24@50 {