video: Export vidconsole_entry_start()

At present this is called only when a newline is detected, since this
indicates the start of a line of text being entered.

Export this function so it can be used by expo, which may start a new
text line itself, without first writing out a newline.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/vidconsole-uclass.c b/drivers/video/vidconsole-uclass.c
index 07427ba..2f3f685 100644
--- a/drivers/video/vidconsole-uclass.c
+++ b/drivers/video/vidconsole-uclass.c
@@ -48,7 +48,7 @@
 	return ops->set_row(dev, row, clr);
 }
 
-static int vidconsole_entry_start(struct udevice *dev)
+int vidconsole_entry_start(struct udevice *dev)
 {
 	struct vidconsole_ops *ops = vidconsole_get_ops(dev);