storm: Add board ID calculation function

storm uses three GPIOs in tertiary mode, such that proto0 returns
value of 8 when the GPIOs are interpreted as a single tertiary number.

Adjust the calculated value to return board ID of 0 on proto0, and
monotonously incrementing values on newer boards.

BUG=chrome-os-partner:30489
TEST=when enabled, the board ID value of zero is reported on the console.

Original-Change-Id: I2ff8fd5cbc8d568877b6f8bf220e146893f1e4be
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/210118
(cherry picked from commit 6ba24f31583933f02be111c8767ae9df56537011)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I35ee218df35a0924d4bb8fcbc6c875450a609f24
Reviewed-on: http://review.coreboot.org/8721
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
2 files changed