yorp: update gpio alternate function parameter
yorp: update gpio alternate function parameter

The NPCX driver doesn't use anything but >= 0; make everything
consistent as to not imply something is different between UART and
everything else.

BRANCH=none
BUG=none
TEST=none

Change-Id: Ib98f56f7004df2405df7d2cc1847f1ed4b3ec558
Signed-off-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/976524
Reviewed-by: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>

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