toshiba_acpi: Add System Configuration Interface

SCI stands for System Configuration Interface,
which aim is to conceal differences in hardware
between different models.

This patch introduces four new calls: sci_open,
sci_close, sci_read and sci_write, along with
its definitions and return codes which will be
used by later patches.

More information about the SCI can be found at
Jonathan Buzzard's website [1].

[1] http://www.buzzard.me.uk/toshiba/docs.html

Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>