RDMA/cma: Combine cma_ndev_work with cma_work

RDMA/cma: Combine cma_ndev_work with cma_work

These are the same thing, except that cma_ndev_work doesn't have a state
transition. Signal no state transition by setting old_state and new_state
== 0.

In all cases the handler function should not be called once
rdma_destroy_id() has progressed passed setting the state.

Link: https://lore.kernel.org/r/20200902081122.745412-6-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>