video: Clear the vidconsole rather than the video

It is better to clear the console device rather than the video device,
since the console has the text display. We also need to reset the cursor
position with the console, but not with the video device.

Add a new function to handle this and update the 'cls' command to use it.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/video_console.h

@@ -285,6 +285,15 @@ int vidconsole_put_string(struct udevice *dev, const char *str);
 void vidconsole_position_cursor(struct udevice *dev, unsigned col,
 				unsigned row);
 
+/**
+ * vidconsole_clear_and_reset() - Clear the console and reset the cursor
+ *
+ * The cursor is placed at the start of the console
+ *
+ * @dev:	vidconsole device to adjust
+ */
+int vidconsole_clear_and_reset(struct udevice *dev);
+
 /**
  * vidconsole_set_cursor_pos() - set cursor position
  *