ec/google/wilco: Add virtual button support

Add an ACPI device that is compatible with the Intel Virtual
Button kernel driver for reporting tablet mode state and various
virtual button events that may come from the EC.

This driver is used in Windows and in the Linux kernel at
drivers/platform/x86/intel-vbtn.c

Because of a check in the kernel driver it expects the board to
define the SMBIOS enclosure type as convertible for the check at
driver load time for tablet/laptop and dock/undock to work.

The virtual tablet mode button will proxy the tablet mode state
sent from the Sensor Hub to a SW_TABLET_MODE event in the kernel.

The virtual power button is used during S0ix for the EC to wake
the system with an SCI.  There are separate press and release
events which are sent for completeness, although the kernel driver
will ignore the release event.

BUG=b:73137291
TEST=Test that the power button can wake the system from S0ix.
Also verify that the device is reported as laptop mode at boot.

Change-Id: I0d5dc985a3cfb1d01ff164c4e67f17e6b1cdd619
Signed-off-by: Duncan Laurie <dlaurie@google.com>
---
M src/ec/google/wilco/acpi/ec.asl
M src/ec/google/wilco/acpi/ec_ram.asl
M src/ec/google/wilco/acpi/event.asl
A src/ec/google/wilco/acpi/vbtn.asl
4 files changed, 116 insertions(+), 0 deletions(-)