irqchip: nvic: Use the generic noop function

Using the generic function saves looking up this custom one in a source
navigator.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lkml.kernel.org/r/1401894112-13386-1-git-send-email-daniel.thompson@linaro.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>