serial: make serial_stub_* to static functions

Add missing static to serial_stub_puts().

Unexport serial_stub_{getc,tstc} because they are used locally.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/serial/serial-uclass.c b/drivers/serial/serial-uclass.c
index a9c4f89..200f4b9 100644
--- a/drivers/serial/serial-uclass.c
+++ b/drivers/serial/serial-uclass.c
@@ -212,27 +212,30 @@
 {
 }
 
-#if defined(CONFIG_DM_STDIO) && CONFIG_IS_ENABLED(SERIAL_PRESENT)
+#if defined(CONFIG_DM_STDIO)
+
+#if CONFIG_IS_ENABLED(SERIAL_PRESENT)
 static void serial_stub_putc(struct stdio_dev *sdev, const char ch)
 {
 	_serial_putc(sdev->priv, ch);
 }
 #endif
 
-void serial_stub_puts(struct stdio_dev *sdev, const char *str)
+static void serial_stub_puts(struct stdio_dev *sdev, const char *str)
 {
 	_serial_puts(sdev->priv, str);
 }
 
-int serial_stub_getc(struct stdio_dev *sdev)
+static int serial_stub_getc(struct stdio_dev *sdev)
 {
 	return _serial_getc(sdev->priv);
 }
 
-int serial_stub_tstc(struct stdio_dev *sdev)
+static int serial_stub_tstc(struct stdio_dev *sdev)
 {
 	return _serial_tstc(sdev->priv);
 }
+#endif
 
 /**
  * on_baudrate() - Update the actual baudrate when the env var changes