RDMA/rtrs-clt: Remove duplicated switch-case handling for CM error events

The events returning the same error value are put together.

Link: https://lore.kernel.org/r/20201023074353.21946-9-jinpu.wang@cloud.ionos.com
Signed-off-by: Gioh Kim <gi-oh.kim@cloud.ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>