nvmet-rdma: Fix REJ status code

nvmet_sq_init() returns a value <= 0. nvmet_rdma_cm_reject() expects
a second argument that is a NVME_RDMA_CM_* constant. Hence this patch.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Sagi Grimberg <sagi@grimbeg.me>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>