google/banon: add new board as variant of cyan baseboard

Add support for google/banon (Acer Chromebook 15 CB3-531) as
a variant of the cyan Braswell baseboard.

- Add board-specific code as the new banon variant

Sourced from Chromium branch firmware-strago-7287.B,
commit 02dc8db: Banon: 2nd source DDR memory (Micro-MT52L256M32D1PF)

Change-Id: If29e95deee88b79522547e16fc80c2d5378da7c7
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/21571
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
11 files changed