toshiba_acpi: Add full hotkey support

Calling the ENAB method on Toshiba laptops results in notifications being
sent when laptop hotkeys are pressed.  This patch simply calls that method
and sets up an input device if it's successful.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>