genirq/affinity: Don't pass irq_affinity_desc array to irq_build_affinity_masks

Prepare for abstracting irq_build_affinity_masks() into a public function
for assigning all CPUs evenly into several groups.

Don't pass irq_affinity_desc array to irq_build_affinity_masks, instead
return a cpumask array by storing each assigned group into one element of
the array.

This allows to provide a generic interface for grouping all CPUs evenly
from a NUMA and CPU locality viewpoint, and the cost is one extra allocation
in irq_build_affinity_masks(), which should be fine since it is done via
GFP_KERNEL and irq_build_affinity_masks() is a slow path anyway.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20221227022905.352674-4-ming.lei@redhat.com