Provide a function to run the Vesa BIOS for a given PCI device and obtain
the resulting configuration (e.g. display size) for use by the video
uclass. This makes it easier to write a video driver that uses vesa and
supports driver model.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>