dm: video: Add basic ANSI escape sequence support

Really just the subset that is needed by efi_console.  Perhaps more will
be added later, for example color support would be useful to implement
efi_cout_set_attribute().

Signed-off-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/include/video.h b/include/video.h
index 5b4e78b..61ff653 100644
--- a/include/video.h
+++ b/include/video.h
@@ -115,6 +115,13 @@
 int video_reserve(ulong *addrp);
 
 /**
+ * video_clear() - Clear a device's frame buffer to background color.
+ *
+ * @dev:	Device to clear
+ */
+void video_clear(struct udevice *dev);
+
+/**
  * video_sync() - Sync a device's frame buffer with its hardware
  *
  * Some frame buffers are cached or have a secondary frame buffer. This