c2d2: add vref detection console command
c2d2: add vref detection console command

In order to support plugging in DUT power after running
flash_ec, we need a way to poll for H1 Vref on DUT.

BRANCH=servo
BUG=b:150796623
TEST=flash_ec waits until power in inserted

Signed-off-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>
Change-Id: Ie597a6de06a35f48a93ac1615eebd2ef259ed341
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2090084
Commit-Queue: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>

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