acer-wmi: Add debugfs file for device detection

acer-wmi: Add debugfs file for device detection

Add a debugfs file for showing the full results of the method we use to
detect devices on WMID laptops.

This should be useful in the case that a Linux user gets an Acer laptop
with 3G support (and/ or people who enjoy ripping their wireless cards out)
so we can get some feedback on how this value changes in these cases.

(At the moment, we always enable the wireless and 3G control. In the case
of the former, this is fairly safe. In the case of the latter though,
trying to toggle this device if it doesn't exist on a laptop causes ACPI
warnings/ errors).

To summarise: If you have an Acer laptop with a built in 3G card, please
report back the value from this file.

Signed-off-by: Carlos Corbacho <carlos@strangeworlds.co.uk>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>