genriq: pick only one CPU while overriding the affinity during migration

With commit bfc60d474137 ("genirq: Use irq_set_affinity_locked to change
irq affinity"), affinity listeners receive the notification when the irq
affinity is changed during migration. If there is no online and
un-isolated CPU available from the user specified affinity, the affinity
is overridden with all online and un-isolated CPUs. The same cpumask is
notified to PM QOS affinity listener which applies PM_QOS_CPU_DMA_LATENCY
vote to all those CPUs. As the low level irqchip driver sets affinity to
only one CPU, do the same while overriding the affinity during migration.

Change-Id: I0bcb75dd356658da100fbeeefd33ef8b121f4d6d
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>