ARM: dts: at91: sama5d4_xplained: change the key code of the gpio key

Having a button code and not a key code causes issues with libinput.
udev won't set ID_INPUT_KEY. If it is forced, then it causes a bug
within libinput.

Signed-off-by: Ludovic Desroches <[e-mail]>
Signed-off-by: Nicolas Ferre <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/arm/boot/dts/at91-sama5d4_xplained.dts

···
  */
 /dts-v1/;
 #include "sama5d4.dtsi"
+#include <dt-bindings/input/input.h>
 
 / {
 	model = "Atmel SAMA5D4 Xplained";
···
 		pb_user1 {
 			label = "pb_user1";
 			gpios = <&pioE 8 GPIO_ACTIVE_HIGH>;
-			linux,code = <0x100>;
+			linux,code = <KEY_PROG1>;
 			wakeup-source;
 		};
 	};