style: boards: comply with MISRA C:2012 Rule 15.6

Add missing braces to comply with MISRA C:2012 Rule 15.6 and
also following Zephyr's style guideline.

Signed-off-by: Pisit Sawangvonganan <[email protected]>

Author: ndrs-pst

boards/silabs/dev_kits/sltb010a/board.c

@@ -33,8 +33,9 @@ static int thunderboard_init(void)
 		return -ENODEV;
 	}
 	ret = gpio_pin_configure_dt(&wake_up_gpio_dev, GPIO_OUTPUT_ACTIVE);
-	if (ret < 0)
+	if (ret < 0) {
 		return ret;
+	}
 
 	return 0;
 }

boards/silabs/dev_kits/xg24_dk2601b/board.c

@@ -33,8 +33,9 @@ static int efr32xg24_dk2601b_init(void)
 		return -ENODEV;
 	}
 	ret = gpio_pin_configure_dt(&wake_up_gpio_dev, GPIO_OUTPUT_ACTIVE);
-	if (ret < 0)
+	if (ret < 0) {
 		return ret;
+	}
 
 	return 0;
 }

boards/silabs/dev_kits/xg27_dk2602a/board.c

@@ -33,8 +33,9 @@ static int dev_kit_init(void)
 		return -ENODEV;
 	}
 	ret = gpio_pin_configure_dt(&wake_up_gpio_dev, GPIO_OUTPUT_ACTIVE);
-	if (ret < 0)
+	if (ret < 0) {
 		return ret;
+	}
 
 	return 0;
 }