Merge pull request #7856 from kYc0o/fix_driver_adcxx1c_unused_arg

tests/driver_adcxx1c: fix warning unused  argument

tests/driver_adcxx1c/main.c

@@ -30,6 +30,7 @@ static adcxx1c_t dev;
 
 static void alert_cb(void *arg)
 {
+    (void)arg;
     puts("[Alert]\n");
 }