RDMA/cma: Fix hang when cma_netevent_callback fails to queue_work

In the Linux kernel, the following vulnerability has been resolved:

RDMA/cma: Fix hang when cma_netevent_callback fails to queue_work

The cited commit fixed a crash when cma_netevent_callback was called for

a cma_id while work on that id from a previous call had not yet started.

The work item was re-initialized in the second call, which corrupted the

work item currently in the work queue.

However, it left a problem when queue_work fails (because the item is

still pending in the work queue from a previous call). In this case,

cma_id_put (which is called in the work handler) is therefore not

called. This results in a userspace process hang (zombie process).

Fix this by calling cma_id_put() if queue_work fails.