irqchip/armada-370-xp: Make IPIs use handle_percpu_devid_irq()

As done for the Arm GIC irqchips, move IPIs to handle_percpu_devid_irq() as
handle_percpu_devid_fasteoi_ipi() isn't actually required.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201109094121.29975-3-valentin.schneider@arm.com