MSI S270 Laptop support: backlight, wlan, bluetooth states

Create a driver to support the platform-specific features
of MSI S270 laptops (and maybe other MSI laptops).
This driver implements a backlight device for controlling LCD brightness
(/sys/class/backlight/msi-laptop-bl/).
In addition it allows access to the WLAN and Bluetooth states
through a platform driver (/sys/devices/platform/msi-laptop-pf/).

Signed-off-by: Lennart Poettering <mzxreary@0pointer.de>
Cc: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>