boards: arm: stm32u5a9j-dk: fix switch gpio config

The user switch on the board require a pull down on mcu side and
is active high.

Signed-off-by: Guillaume Galeazzi <[email protected]>

Author: gzzi

boards/arm/stm32u5a9j_dk/stm32u5a9j_dk.dts

@@ -37,7 +37,7 @@
 		compatible = "gpio-keys";
 		user_button: button_0 {
 			label = "User";
-			gpios = <&gpioc 13 GPIO_ACTIVE_LOW>;
+			gpios = <&gpioc 13 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>;
 			zephyr,code = <INPUT_KEY_0>;
 		};
 	};