x86: coreboot: Add a sysinfo driver

Create a sysinfo driver to avoid needing a custom checkboard()
function. With this the following information is printed when booting
from coreboot under QEMU:

   Model: Standard PC (i440FX + PIIX, 1996)
   Manufacturer: QEMU
   Prior-stage version: 4.21-885-g2a87ef1eca56
   Prior-stage date: 11/11/2023

Signed-off-by: Simon Glass <sjg@chromium.org>