This fixes a regression for the Nomadik on the main system
timers.

The Nomadik seemed a bit slow and its heartbeat wasn't looking
healthy. And it was not strange, because it has been connected
to the 32768 Hz clock at boot, while being told by the clock driver
that it was 2.4MHz. Actually connect the TIMCLK to 2.4MHz by
default as this is what we want for nice scheduling, clocksource
and clock event.

Cc: stable@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>