nvme-rdma: minor cleanup in nvme_rdma_create_cq()

Before cleanup:
enum ib_poll_context poll_ctx;

if (nvme_rdma_poll_queue(queue)) {
        poll_ctx = IB_POLL_DIRECT;
        queue->ib_cq = ib_alloc_cq(ibdev, queue, queue->cq_size,
                                   comp_vector, poll_ctx);
} else {
        poll_ctx = IB_POLL_SOFTIRQ;
        queue->ib_cq = ib_cq_pool_get(ibdev, queue->cq_size,
                                      comp_vector, poll_ctx);
}

After cleanup:
if (nvme_rdma_poll_queue(queue))
        queue->ib_cq = ib_alloc_cq(ibdev, queue, queue->cq_size,
                                   comp_vector, IB_POLL_DIRECT);
else
        queue->ib_cq = ib_cq_pool_get(ibdev, queue->cq_size,
                                      comp_vector, IB_POLL_SOFTIRQ);

IB_POLL_SOFTIRQ/IB_POLL_SOFTIRQ gets used directly in function, this
seems more accessible.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>