lib/coreboot_table: Show splashscreen in lb_table_init

Every vga init implementation needs to cache the framebuffer state
to be able to fill the lb_framebuffer struct later on in the
fill_lb_framebuffer call. Showing the bootsplash afterwards
guarantees to have the same interface into all the vga drivers.

This is by far from ideal, as it only allows for a single driver at
compile-time and should be adapted in the future.

It was tested on the wip razer blade stealth using vgabios @ 1280x1024
and also in Qemu @ 1280x1024.
By default the qemu framebuffer will be initialized in 800x600@32.
This can be overwriten by configuration by setting
CONFIG_DRIVERS_EMULATION_QEMU_BOCHS_{X,Y}RES .

Change-Id: I4bec06d22423627e8f429c4b47e0dc9920f1464e
Signed-off-by: Johanna Schander <coreboot@mimoja.de>
---
M src/device/Kconfig
M src/device/pci_device.c
M src/include/bootsplash.h
M src/lib/bootsplash.c
M src/lib/coreboot_table.c
5 files changed, 21 insertions(+), 38 deletions(-)