veyron_pinky: Add board ID support

This patch adds code to read the board ID from Pinky and put it into the
coreboot table.

(Note: This implementation differs slightly from Tegra since it pinmuxes
the GPIOs inside board_id(). That means the pinmuxing might be set more
than once if called in multiple stages, which is perfectly harmless and
in my opinion cleaner than having to (remember to) do it manually in one
of the per-stage files.)

BUG=chrome-os-partner:30167
TEST=With depthcharge patch, select -rev1 device tree for board ID 0.

Change-Id: I265fafcb176a31a46f7792ecf352f1671be7dd41
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 9da10ce8b62ec98243fc7c82544b3004316799a8
Original-Change-Id: I5b5689373e1e47b1e0944b5fe5f2e70a285b931f
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/217675
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/8870
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)
3 files changed