soc/intel/skylake: provide poweroff() implementation

Implement poweroff() by putting the chipset into ACPI S5 state.

BUG=chrome-os-partner:54977

Change-Id: I9288dcee13347a8aa3f822ca3d75148ba2792859
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/15688
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins)
1 file changed