nbd: use the atomic queue limits API in nbd_set_size

Use queue_limits_start_update / queue_limits_commit_update to update
all the limits in one go and with proper sanity checking.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240229143846.1047223-4-hch@lst.de


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