toshiba_acpi: Add support for Keyboard functions mode

Recent Toshiba laptops that come with the new keyboard layout have
the Special Functions (hotkeys) enabled by default, which, in order to
access the F{1-12} keys, you need to press the FN-F{1-12} key to
access such key.

This patch adds support to toggle the Keyboard Functions operation
mode by creating the sysfs entry "kbd_functions_keys", accepting only
two parameters, 0 to set the "Normal Operation" mode and 1 to set the
"Special Functions" mode, however, everytime the mode is toggled, a
restart is needed.

In the "Normal Operation" mode, the F{1-12} keys are as usual and
the hotkeys are accessed via FN-F{1-12}.

In the "Special Functions" mode, the F{1-12} keys trigger the hotkey
and the F{1-12} keys are accessed via FN-F{1-12}.

Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>