nvme-rdma: move nvme_rdma_configure_admin_queue code location

We will call it from other places so avoid having to forward declare it.
Also move it next to nvme_rdma_destroy_admin_queue.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>