xprtrdma: Remove the RPC/RDMA QP event handler

Clean up: The handler only recorded a trace event. If indeed no
action is needed by the RPC/RDMA consumer, then the event can be
ignored.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>