Add support driver for Intel Rapid Start Technology

Intel Rapid Start Technology is a firmware-based suspend-to-disk
implementation. Once placed in S3, the device will wake once either a
timeout elapses or the battery reaches a critical level. It will then resume
to the firmware and copy the contents of RAM to a specialised partition, and
then power off the machine. If the user turns the machine back on the
firmware will copy the contents of the partition back to RAM and then resume
from S3 as normal.

This driver provides an interface for configuring the wakeup events and
timeout. It still requires firmware support and an appropriate suspend
partition.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>