This patch makes it possible to configure away the sched_clock
part of the MTU timer.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NMattias Wallin <mattias.wallin@stericsson.com>
Signed-off-by: NJonas Aberg <jonas.aberg@stericsson.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>