ARM: ux500: Provide local timer support for Device Tree

This enables local timer (AKA: private timer) support for
all u8500 based hardware using DT.

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