xprtrdma: Remove qplock

Clean up.

After "xprtrdma: Remove ro_unmap() from all registration modes",
there are no longer any sites that take rpcrdma_ia::qplock for read.
The one site that takes it for write is always single-threaded. It
is safe to remove it.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/verbs.c

@@ -433,7 +433,6 @@ rpcrdma_ia_open(struct rpcrdma_xprt *xprt, struct sockaddr *addr, int memreg)
 	dprintk("RPC:       %s: memory registration strategy is '%s'\n",
 		__func__, ia->ri_ops->ro_displayname);
 
-	rwlock_init(&ia->ri_qplock);
 	return 0;
 
 out3:
@@ -672,10 +671,8 @@ retry:
 			goto out;
 		}
 
-		write_lock(&ia->ri_qplock);
 		old = ia->ri_id;
 		ia->ri_id = id;
-		write_unlock(&ia->ri_qplock);
 
 		rdma_destroy_qp(old);
 		rpcrdma_destroy_id(old);

net/sunrpc/xprtrdma/xprt_rdma.h

@@ -65,7 +65,6 @@
  */
 struct rpcrdma_ia {
 	const struct rpcrdma_memreg_ops	*ri_ops;
-	rwlock_t		ri_qplock;
 	struct ib_device	*ri_device;
 	struct rdma_cm_id 	*ri_id;
 	struct ib_pd		*ri_pd;