Update example, use /dev/input/js0, the first joystick

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

examples/joystick.c

@@ -78,7 +78,7 @@ int main(void)
 	uev_t js1_watcher;
 	uev_ctx_t ctx;
 
-	fd = open("/dev/input/js1", O_RDONLY, O_NONBLOCK);
+	fd = open("/dev/input/js0", O_RDONLY, O_NONBLOCK);
 	if (fd < 0)
 		errx(errno, "Cannot find a joystick attached.");