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>
3 files changed