Use visible size when filling frame buffer

The buffer pixel area is based on nominal framebuffer size rather than
visible area.  On systems like Link, the internal panel size is greater
than the external display size, but the nominal framebuffer size is the
latter.  This means the amount of memory mapping covers a smaller area
than what is actually needed to fill the internal panel.

This patch updates the fill frame buffer code to use the visible area,
which correctly reflects the size of the internal panel.

BUG=chrome-os-partner:16363
TEST=Boot link and daisy with external monitor attached. make sure the
splash screen is fully white.

Change-Id: I6cacef64dfc4542fab7c87ae6613d78929f497a9
Signed-off-by: Simon Que <sque@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/38655
Reviewed-by: St├ęphane Marchesin <marcheu@chromium.org>
4 files changed