soc/intel/apollolake: provide poweroff() implementation

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

BUG=chrome-os-partner:54977

Change-Id: I4ee269f03afd252d4bce909a8cc7c64d6270b16e
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/15686
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins)
1 file changed