toshiba_acpi: Make toshiba_eco_mode_available more robust

Some Toshiba laptops do not come with the ECO led installed, however,
the driver is registering support for it when it should not.

This patch makes the toshiba_eco_mode_available function more robust
in detecting ECO led capabilities, not registering the led on laptops
that do not support it and registering the led when it really does.

The ECO led function now returns 0x8e00 (Not Installed) by querying
with in[3] = 0, whenever theres no physical LED installed, and
returning 0x8300 (Input Data Error) when it is, however, there are
some BIOSes that have stub function calls not returning anything and
and the LED device was being registered too, hence the change of the
default return value from 1 to 0.

Signed-off-by: Azael Avalos <coproscefalo@gmail.com>

Minor comment update, fixed a whitespace error, s/truly/actual/.

Signed-off-by: Darren Hart <dvhart@linux.intel.com>