boards: stm32mp157c_dk2: Add led and button to dts

Add led and button to board description to enable basic gpio
tests.

Signed-off-by: Erwan Gouriou <[email protected]>

Author: erwango

boards/arm/stm32mp157c_dk2/stm32mp157c_dk2.dts

@@ -24,6 +24,28 @@
 		zephyr,flash = &retram;
 		zephyr,sram = &mcusram;
 	};
+
+	leds {
+		compatible = "gpio-leds";
+		red_led_1: led_1 {
+			gpios = <&gpioh 7 GPIO_ACTIVE_HIGH>;
+			label = "LD7";
+		};
+	};
+
+	gpio_keys {
+		compatible = "gpio-keys";
+		user_button: button {
+			label = "User 1";
+			gpios = <&gpioa 14 GPIO_ACTIVE_LOW>;
+		};
+	};
+
+	aliases {
+		led0 = &red_led_1;
+		sw0 = &user_button;
+	};
+
 };
 
 &spi4{