cyclic: invoke uthread_schedule() from schedule()

cyclic: invoke uthread_schedule() from schedule()

Make the schedule() call from the CYCLIC framework a uthread scheduling
point too. This makes sense since schedule() is called from a lot of
places where uthread_schedule() needs to be called.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Stefan Roese <sr@denx.de>