v3/ec: Updates for Proto 1

* Update SYSMON signal mappings to include the new current monitors
and VREF for those monitors, remove unused signal.
* Update devicetree for new GPIO pins for controlling power on the
IT68051, and for muxing the HPD signals to choose between the STM32,
the FPGA, and the IT68051.
* Add documentation of where the HPD signal can be generated, and
how it is routed to the HDMI and DisplayPort connectors.

TEST=Build and load. Run the ad-hoc tests in README.md

Change-Id: I8cd3465cdaf4d8d71026c88c8cd39b8d62f4115d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/chameleon/+/2826034
Reviewed-by: Alexandru M Stan <amstan@chromium.org>
Commit-Queue: Paul Fagerburg <pfagerburg@chromium.org>
Tested-by: Paul Fagerburg <pfagerburg@chromium.org>
9 files changed