mb/lenovo/r500: Add mainboard

Tested:
- Ethernet NIC
- Wifi RFKill
- USB
- LVDS, VGA with libgfxinit
- Booting with dock attached (COM1)
- Keyboard, trackpoint
- SeaBIOS 1.10.3
- S3 resume (Needs SeaBIOS with sercon disabled)
- Tested in descriptor mode, with vendor FD and ME

Untested:
- SATA (likely works)
- Trackpad (my cable is broken, likely works)
- Displayport (likely works)
- Descriptorless mode
- DVD drive
- Extra battery

Does not work:
- Dock hotplug
- Quad core CPU (hangs during AP init, probably needs hardware mod)
- Models with a sole ATI GPU (needs probing of PEG in romstage)
- Hotplugging the expresscard slot (works with 'echo 1 | sudo tee
/sys/bus/pci/rescan')

TODO:
- proper dock support
- documentation

note: This board was hard to flash, I had to desolder the flash.

TESTED: on a R500 with an Intel iGPU, SeaBIOS 1.10.3, Debian 9, Linux 4.9

Change-Id: I9e129b2e916acdf2b8534fa9d8d2cfc8f64f5815
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
---
M src/mainboard/lenovo/t400/Kconfig
M src/mainboard/lenovo/t400/Kconfig.name
M src/mainboard/lenovo/t400/Makefile.inc
M src/mainboard/lenovo/t400/devicetree.cb
M src/mainboard/lenovo/t400/dsdt.asl
A src/mainboard/lenovo/t400/variants/r500/Makefile.inc
A src/mainboard/lenovo/t400/variants/r500/data.vbt
A src/mainboard/lenovo/t400/variants/r500/gpio.c
A src/mainboard/lenovo/t400/variants/r500/overridetree.cb
A src/mainboard/lenovo/t400/variants/t400/Makefile.inc
R src/mainboard/lenovo/t400/variants/t400/gpio.c
A src/mainboard/lenovo/t400/variants/t400/overridetree.cb
12 files changed, 246 insertions(+), 38 deletions(-)