toshiba_acpi: Adapt Illumination code to use SCI

Change the toshiba_illumination_* code to use the
newly introduced SCI functions, making the code
more robust in detecting Illumination capabilities
properly, since it was only opening the SCI and
the return value was never checked for errors or
actual Illumination support.

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