NFSv4: Remove nfs_client->cl_sem

Now that we're using the flags to indicate state that needs to be
recovered, as well as having implemented proper refcounting and spinlocking
on the state and open_owners, we can get rid of nfs_client->cl_sem. The
only remaining case that was dubious was the file locking, and that case is
now covered by the nfsi->rwsem.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/nfs_fs_sb.h

@@ -42,12 +42,6 @@ struct nfs_client {
 	struct rb_root		cl_openowner_id;
 	struct rb_root		cl_lockowner_id;
 
-	/*
-	 * The following rwsem ensures exclusive access to the server
-	 * while we recover the state following a lease expiration.
-	 */
-	struct rw_semaphore	cl_sem;
-
 	struct list_head	cl_delegations;
 	struct rb_root		cl_state_owners;
 	spinlock_t		cl_lock;