mb/clevo/kbl-u: Add Clevo N240BU as variant

This is the board used in the Tuxedo BU1406. The ID of the graphics device
differs.

libgfxinit fails to train the eDP link, and the panel does not light up.

Extracted VBIOS Option ROM has ID 8086,0406.

coreboot is unable to run VBIOS Option ROM (even with disabled device
mismatch).

    Timestamp - Option ROM initialization: 77806110188
    FMAP: area COREBOOT found @ 350200 (4914688 bytes)
    CBFS: Locating 'pci8086,5916.rom'
    CBFS: Found @ offset 11ce00 size 10000
    In CBFS, ROM address for PCI: 00:02.0 = 0xffc6d048
    PCI ROM image, vendor ID 8086, device ID 0406,
    ID mismatch: vendor ID 8086, device ID 5916
    Copying VGA ROM Image from 0xffc6d048 to 0xc0000, 0x10000 bytes
    Timestamp - Option ROM copy done: 77877204844
    Calling Option ROM...
    Unsupported software interrupt #0x15 eax 0x1905f34
    Unsupported software interrupt #0x15 eax 0x5f51
    Unsupported software interrupt #0x15 eax 0x5f40
    Unsupported software interrupt #0x15 eax 0x5f52
    Unsupported software interrupt #0x15 eax 0x5f49
    Unsupported software interrupt #0x15 eax 0x3a95f49
    Unsupported software interrupt #0x15 eax 0x5f14
    Unsupported software interrupt #0x15 eax 0x405f35
    ... Option ROM returned.
    VGA Option ROM was run
    Timestamp - Option ROM run done: 78406420234
    PCI: 00:02.0 init finished in 210 msecs

1.  SeaBIOS initializes the display with VBIOS Option ROM.
1.  TianoCore loaded from SeaBIOS does not run.
1.  Grml from USB boots.
1.  SPI Flash Console works.

Change-Id: I57dc2db78c66dd93642f41d10343d1be05fb9f17
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
---
M src/mainboard/clevo/kbl-u/Kconfig
M src/mainboard/clevo/kbl-u/Kconfig.name
A src/mainboard/clevo/kbl-u/variants/n240bu/data.vbt
A src/mainboard/clevo/kbl-u/variants/n240bu/devicetree.cb
A src/mainboard/clevo/kbl-u/variants/n240bu/gma-mainboard.ads
A src/mainboard/clevo/kbl-u/variants/n240bu/hda_verb.c
A src/mainboard/clevo/kbl-u/variants/n240bu/include/gpio_table.h
7 files changed, 862 insertions(+), 3 deletions(-)