Input: add driver for Fujitsu application buttons

This driver supports the application buttons on some Fujitsu Lifebook
laptops.  It is based on the earlier apanel driver done by Jochen Eisenger,
but with many changes.  The original driver used ioctl's and a separate
user space program (see http://apanel.sourceforge.net).  This driver hooks
into the input subsystem so that the normal keys act as expected without a
daemon.  In addition to buttons, the Mail Led is handled via LEDs class
device.

The driver now supports redefinable keymaps and no longer has to have a DMI
table for all Fujitsu laptops.

I thought about mixing this driver should be integrated into the Fujitsu
laptop extras driver that handles backlight, but rejected the idea because
it wasn't clear if all the Fujitsu laptops supported both.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>