ARM: ux500: Remove empty function u8500_of_init_devices()

As promised, now all devices which resided in u8500_of_init_devices()
have been enabled for Device Tree, we can completely remove it.

Acked-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>