clocksource: nomadik-mtu: support timer-based delay

This patch adds support to use Nomadik MTU for timer-based delay.

Acked-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>