clocksource/drivers/imx: Allow timer irq affinity change

Allow the timer core to change the smp affinity of the broadcast timer
irq by setting CLOCK_EVT_FEAT_DYNIRQ flag. For this to work the timer
core needs to be told about the used irq.

This reduces interrupt pressure and wakeups on CPU0 as well as vastly
reducing the number of timer broadcast IPIs.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>