ARM: shmobile: koelsch: Use keyboard as gpio-keys node name

This appears to be the best match for ePAPR.
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7791-koelsch.dts

@@ -44,7 +44,7 @@
 		#size-cells = <1>;
 	};
 
-	gpio-keys {
+	keyboard {
 		compatible = "gpio-keys";
 
 		key-1 {