nvme-tcp: remove nvme_tcp_destroy_io_queues()

Now when destroying the IO queue we call nvme_tcp_stop_io_queues()
twice, nvme_tcp_destroy_io_queues() has an unnecessary call. Here we
try to remove nvme_tcp_destroy_io_queues() and merge it into
nvme_tcp_teardown_io_queues(), simplify the code and align with
nvme-rdma, make it easy to maintaince.

Signed-off-by: Chunguang.xu <chunguang.xu@shopee.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>