ARM: versatile: add the syscon LEDs to the DT

The device tree version of Versatile AP/PB never had LED support
so we are missing LEDs from our hardware boards. Add this as
syscon LEDs like we did for Integrator and Juno. We need to
spawn devices in the syscon with "simple-mfd" for this to work.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>