mb/lenovo/x220: Add x1 as a variant

ThinkPad X1 ( https://www.thinkwiki.org/wiki/Category:X1 ) is nearly a
clone of X220, with additional USB3 controller on pci-e (as i7 variant
of x220), and a powered ESATA port wired to ata4 (Linux' annotation).

Documentation added.

Tested:
- CPU i5-2520M
- Slotted DIMM 8GiB
- Camera
- Mini pci-e on wlan slot
- Msata on wwan slot
- On board SDHCI connected to pci-e
- USB3 controller connected to pci-e
- NVRAM options for North and South bridges
- S3
- TPM1 on LPC
- Linux 4.9.110-3 within Debian GNU/Linux stable, loaded from
  SeaBIOS, or Linux payload (Heads)

Not tested:
- Fingerprint reader on USB2
- Onboard USB2 interfaces (wlan slot, wwan slot)

Change-Id: Ibbc45f22c63b77ac95c188db825d0d7e2b03d2d1
Signed-off-by: Bill XIE <persmule@gmail.com>
Reviewed-on: https://review.coreboot.org/c/29434
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

1 files changed, 0 insertions, 0 deletions

diff --git a/Documentation/mainboard/lenovo/x1_flash_ic.jpg b/Documentation/mainboard/lenovo/x1_flash_ic.jpg
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