Document kgpe-d16 usage and boards options

Things are scattered around. Some drops.

• https://github.com/osresearch/heads/pull/867 has been brought back (coreboot 4.11 with TPM 1.2 support for workstation, workstation-usb and server (last one not enough tested in current state)
• https://github.com/osresearch/heads/issues/134#issuecomment-368922440 documentation should be under wiki
• https://github.com/u-root/u-bmc/issues/133 for replacement of old an unmaintained openbmc code (part of funding path)
• Is the newer flashrom still working to flash the bmc to flash it from heads?
• No TPM2 14-1 pins boards avail? (prospection https://github.com/osresearch/heads/pull/893/)
• 16MB SPI: W25Q128FVSG SOP8 chip soldered on top of a SOP8 SO8 SOIC8 TO DIP8 adapter

Insurgo decided to fund KGPE-D16 upstreaming efforts. Donations welcome over open collective.

EDIT:

• Current state by community work: https://github.com/osresearch/heads/issues/719#issuecomment-743802259
• Immunefi is funding KGPE-D16 upstreaming effort: https://github.com/osresearch/heads/issues/719#issuecomment-893024079

Start by reviewing the linked Heads issues and pull requests, especially the current-state discussion in issue 719 and the wiki-documentation reference in issue 134. Consolidate the KGPE-D16 usage, board options, and related community work into the wiki, with the linked coreboot, flashrom, OpenBMC, and hardware references preserved.