alienware-wmi: Add support for deep sleep control.

Allow for user configuration of BIOS settings that allow the system to be
turned on via HID devices.

The feature requires hardware architectural modifications and can not be
supported on existing systems.

Signed-off-by: Mario Limonciello <mario_limonciello@dell.com>
[dvhart: comment formatting and line length fixes]
Signed-off-by: Darren Hart <dvhart@linux.intel.com>