x86: add TS-5500 platform support

The Technologic Systems TS-5500 is an x86-based (AMD Elan SC520) single
board computer. This driver registers most of its devices and exposes
sysfs attributes for information such as jumpers state or presence of
some of its features.

This driver currently registers the TS-5500 platform, its on-board LED,
3 pin (GPIO) blocks and its analog/digital converter. It can be extended
to support other Technologic Systems products, such as the TS-5600.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>