[coreboot] Management engine firmware

[Vladimir 'φ-coder/phcoder' Serbinenko]

Hello, all. In order to build X201 rom, you need management engine
firmware. For chromebook the appropriate blobs are in 3rdparty repo, I
suppose supplied by Intel. The only place where I could get ME firmware
for X201 is by dumping chip with external programmer. It's probably not
appropriate for coreboot to distribute those blobs (I'm unsure on their
license) and given that it writes a log to its section which may contain
private data, I don't want to distribute it either. Yet without this
blob the build legitimately fails. Any suggestions on handling this?