fix: ENABLE_SERIAL conditional compilation

src/main.cpp

@@ -178,7 +178,7 @@ int main() {
         .speed = TUSB_SPEED_FULL
     };
     tusb_init(BOARD_TUD_RHPORT, &dev_init);
-#ifndef ENABLE_SERIAL
+#if !ENABLE_SERIAL
     tud_disconnect();
 #endif
     board_init_after_tusb();
@@ -192,7 +192,7 @@ int main() {
     }
     cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, false);
 
-#ifndef ENABLE_SERIAL
+#if !ENABLE_SERIAL
     if (watchdog_caused_reboot()) {
         printf("Rebooted by Watchdog!\n");
         // 当崩溃重启以后，闪三下灯
@@ -219,12 +219,12 @@ int main() {
 
     audio_init();
 
-#ifndef ENABLE_SERIAL
+#if !ENABLE_SERIAL
     watchdog_enable(1000, true);
 #endif
 
     while (1) {
-#ifndef ENABLE_SERIAL
+#if !ENABLE_SERIAL
         watchdog_update();
 #endif
         cyw43_arch_poll();