ARM: dts: kzm9g: Configure NMI key as wake-up source

Add a GPIO key with wake-up capability for the NMI button.
This allows to wake up the system from s2ram without relying on the
buttons on the optional switch board.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/sh73a0-kzm9g.dts

@@ -149,6 +149,13 @@
 			label = "SW1";
 			wakeup-source;
 		};
+
+		wakeup-key {
+			gpios = <&pfc 159 GPIO_ACTIVE_LOW>;
+			linux,code = <KEY_WAKEUP>;
+			label = "NMI";
+			wakeup-source;
+		};
 	};
 
 	sound {