x86: Add Video BIOS Table (VBT) related Kconfig options

This adds Kconfig options for Video BIOS Table which is normally
required if you are using an Intel FSP firmware that is complaint
with spec 1.1 or later to initialize the integrated graphics device.

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