blk-zoned: Split queue_zone_wplugs_show()

Reduce the indentation level of the code in queue_zone_wplugs_show() by
moving the body of the loop in that function into a new function.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20241217210310.645966-5-bvanassche@acm.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>