mainboard/lenovo/x230: Add ThinkPad x230s as a variant

The code is based on autoport and that for X230. Major differences are:
    - Only one DDR3 slot
    - HM77 PCH
    - M.2 socket instead of mini pci-e
    - no docking
    - no tpm

Tested:
    - CPU i5-3337U
    - Slotted DIMM 8GiB
    - Camera
    - pci-e and usb2 on M.2 slot with A key for wlan
    - sata and usb2  (no superspeed components) on M.2 slot with B key for wwan
    - On board SDHCI connected to pci-e
    - USB3 ports
    - libgfxinit-based graphic init
    - NVRAM options for North and South bridges
    - Sound
    - Thinkpad EC
    - S3
    - Linux 4.9 within Debian GNU/Linux stable, loaded from
      Seabios.

Untested:
    - Touch screen, which is said to work under ubuntu but not debian.

Change-Id: Ie537645d5ffaee799e79af2f821f80c3ebd2dfec
Signed-off-by: Bill XIE <persmule@hardenedlinux.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41168
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/Documentation/mainboard/lenovo/Ivy_Bridge_series.md b/Documentation/mainboard/lenovo/Ivy_Bridge_series.md
index f4f0efff6c..5f151663c4 100644
--- a/Documentation/mainboard/lenovo/Ivy_Bridge_series.md
+++ b/Documentation/mainboard/lenovo/Ivy_Bridge_series.md
@@ -1,6 +1,6 @@
 # Lenovo Ivy Bridge series
 
-This information is valid for all supported models, except T430s and T431s.
+This information is valid for all supported models, except T430s, [T431s](t431s.md) and [X230s](x230s.md).
 
 ## Flashing coreboot
 ```eval_rst