ARM/cpuidle: remove __init tag from Calxeda cpuidle probe function

Commit 60a66e37

 changed the Calxeda
cpuidle driver to a platform driver, copying the __init tag from the
_init() to the newly used _probe() function. However, "probe should
not be __init." (Rob said ;-)
Remove the __init tag to fix a section mismatch in the Calxeda
cpuidle driver.

Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>