asurada: enable 1.8v selection for 1.8v signals
asurada: enable 1.8v selection for 1.8v signals

This change enables 1.8v selection for signals which are 1.8v to
prevent leakage in chip.

This change also change NC pins of ADC to output low due to they
don't have pull-down capability.

BUG=b:173490375
BRANCH=none
TEST=save ~3.5mw on asurada.

Signed-off-by: Dino Li <338d523ecf3700bd86eb9c34d220f91911d2a18c@ite.com.tw>
Change-Id: Ib31bd78beeda735ba49e3582b0c0dbb658c8c209
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2606180
Reviewed-by: Ayo Wu <b10f6385124610e90dc8d1e0bec4988d7b599771@google.com>
Reviewed-by: Eric Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec