mb/dell: Add Dell Optiplex 790

This port was generated by autoport and has been tweaked (see below)

There are (at least) three different mainboards:

 - DT:   4 RAM slots, PEG, PCIe x1, PCI, PCIe x16
 - MT:	 4 RAM slots, PEG, PCIe x1, PCI, PCIe x16
 - SFF:  4 RAM slots, PEG, PCIe x16
 - USFF: 2 RAM slots, mPCIe

The variants have different PCI/PCIe configurations and are not
exactly compatible towards each other.

This port has been tested with: SFF, USFF

What works:
 - Booting Arch Linux with kernel 5.2.3-arch1-1-ARCH
 - PCIe (Hotplug on PCIe X1 only!)
 - Onboard graphics with libgfxinit (via VGA)
 - Turning on and off (S5)
 - Harddrive activity LED
 - Onboard sound
 - Onboard ethernet
 - SATA (hotplug)
 - IOMMU
 - Suspend/resume (S3)
 - EHCI debug (rear side, bottom port on the block with ethernet)

What does not work:
 - SuperI/O (Chip is a SCH5544-NS)
    - Serial port
    - PS/2
    - Fan control (fans go to full speed)

 - VBT is missing

Further notes:
 - Default IFD settings block reads/writes to some regions. This can be
   bypassed by plugging the SERVICE_MODE jumper. BIOS version A05 does
   not set any protected ranges, so internal flashing is possible (use a
   layout if the SERVICE_MODE jumper is not plugged).
 - Setting the jumper slows down the boot process of coreboot significantly,
   as coreboot waits 900ms for the ME to report an OK DRAM (which doesn't
   happen with the jumper set)
 - The controller that controls the POST code LEDs on the front of the
   case (likely the SuperIO) stays on slow blinking POST 234, corrupt or
   defect BIOS according to [1].
 - The mainboard has one SOIC16 8192KiB and one SOIC8 2048KiB BIOS chip
   that are recognized as one "Opaque flash chip" of 10240K in size.

[1] http://www.dell.com/support/article/us/en/04/sln284978/a-reference-guide-to-the-dell-optiplex-diagnostic-indicators?lang=en

Change-Id: If3d3a13163d5da1368259a7498019d42fb3ed57f
Signed-off-by: Christoph Pomaska <github@aufmachen.jetzt>
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
---
A Documentation/mainboard/dell/optiplex790.md
A Documentation/mainboard/dell/servicemode.md
M Documentation/mainboard/index.md
A src/mainboard/dell/Kconfig
A src/mainboard/dell/Kconfig.name
A src/mainboard/dell/optiplex_790/Kconfig
A src/mainboard/dell/optiplex_790/Kconfig.name
A src/mainboard/dell/optiplex_790/Makefile.inc
A src/mainboard/dell/optiplex_790/acpi/ec.asl
A src/mainboard/dell/optiplex_790/acpi/platform.asl
A src/mainboard/dell/optiplex_790/acpi/superio.asl
A src/mainboard/dell/optiplex_790/acpi_tables.c
A src/mainboard/dell/optiplex_790/board_info.txt
A src/mainboard/dell/optiplex_790/dsdt.asl
A src/mainboard/dell/optiplex_790/gma-mainboard.ads
A src/mainboard/dell/optiplex_790/hda_verb.c
A src/mainboard/dell/optiplex_790/mainboard.c
A src/mainboard/dell/optiplex_790/romstage.c
A src/mainboard/dell/optiplex_790/variants/optiplex_790_mt-sff/devicetree.cb
A src/mainboard/dell/optiplex_790/variants/optiplex_790_mt-sff/gpio.c
A src/mainboard/dell/optiplex_790/variants/optiplex_790_mt-sff/hda_verb.c
A src/mainboard/dell/optiplex_790/variants/optiplex_790_usff/devicetree.cb
A src/mainboard/dell/optiplex_790/variants/optiplex_790_usff/gpio.c
A src/mainboard/dell/optiplex_790/variants/optiplex_790_usff/hda_verb.c
24 files changed, 1,220 insertions(+), 0 deletions(-)