arm: irq: Notify affinity change when migrating IRQs during hotplug

Hotplug causes IRQs affine to a core that is being taken down to migrate
to an online core. This is done by directly calling the irq_set_affinity
associated with the irq_chip structure. Instead using the
irq_set_affinity() api lets the notifications bubble through.

Change-Id: I81340dc6643a8217518212b9fc949c9a808aea05
Signed-off-by: Praveen Chidambaram <pchidamb@codeaurora.org>