genirq/affinity: Rename *node_to_possible_cpumask as *node_to_cpumask

genirq/affinity: Rename *node_to_possible_cpumask as *node_to_cpumask

The following patches will introduce two stage irq spreading for improving
irq spread on all possible CPUs.

No functional change.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Link: https://lkml.kernel.org/r/20180308105358.1506-2-ming.lei@redhat.com