lib/edid_fill_fb: Support multiple framebuffers

Currently it's not possible to add multiple graphics driver into
one coreboot image. This patch series will fix this issue by providing
a single API that multiple graphics driver can use.

This is required for platforms that have two graphic cards, but
different graphic drivers, like Intel+Aspeed on server platforms or
Intel+Nvidia on consumer notebooks.

The goal is to remove duplicated fill_fb_framebuffer(), the advertisment
of multiple indepent framebuffers in coreboot tables, and better
runtime/build time graphic configuration options.

Add an implementation in edid_fill_fb that supports registering
multiple framebuffers, each with it's own configuration.

As the current code is only compiled for a single graphics driver
there's no change in functionality.

Tested on:
* QEMU VGA cirrus
* QEMU VGA bochs
* Aspeed AST2500 NGI
* Lenovo X220 using libgfxinit
* Intel FSP2.0 GOP

Change-Id: I7264c2ea2f72f36adfd26f26b00e3ce172133621
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
M src/include/edid.h
A src/include/framebuffer_info.h
M src/lib/edid_fill_fb.c
M src/mainboard/google/kukui/mainboard.c
4 files changed, 199 insertions(+), 64 deletions(-)