nyan: Remove non-ternary tristate mode, make ternaries easier

Porting the "gpio_get_tristates()" function from coreboot CL:219901.
It gets more easier than expand board ID to the specify number.

TEST=tested with command "mosys platform version" on big

Change-Id: Ie955b4ccf3b468fd35ff862cc143fc4d18d64c9f
Reviewed-on: https://chromium-review.googlesource.com/228421
Tested-by: Neil Chen <neilc@nvidia.com>
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Commit-Queue: Neil Chen <neilc@nvidia.com>
3 files changed