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 <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>

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

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