RDMA/rxe: Use driver_unregister and new unregistration API

rxe does not have correct locking for its registration/unregistration
paths, use the core code to handle it instead. In this mode
ib_unregister_device will also do the dealloc, so rxe is required to do
clean up from a callback.

The core code ensures that unregistration is done only once, and generally
takes care of locking and concurrency problems for rxe.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/sw/rxe/rxe_loc.h

@@ -232,7 +232,7 @@ int rxe_srq_from_attr(struct rxe_dev *rxe, struct rxe_srq *srq,
 		      struct ib_srq_attr *attr, enum ib_srq_attr_mask mask,
 		      struct rxe_modify_srq_cmd *ucmd);
 
-void rxe_release(struct kref *kref);
+void rxe_dealloc(struct ib_device *ib_dev);
 
 int rxe_completer(void *arg);
 int rxe_requester(void *arg);