block: move max_{open,active}_zones to struct queue_limits

block: move max_{open,active}_zones to struct queue_limits

The maximum number of open and active zones is a limit on the queue
and should be places there so that we can including it in the upcoming
queue limits batch update API.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>