SUNRPC: clean up rpc_setup_pipedir()

There is still a little wart or two there: Since we've already got a
vfsmount, we might as well pass that in to rpc_create_client_dir.
Another point is that if we open code __rpc_lookup_path() here, then we can
avoid looking up the entire parent directory path over and over again: it
doesn't change.

Also get rid of rpc_clnt->cl_pathname, since it has no users...

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

include/linux/sunrpc/clnt.h

@@ -51,7 +51,6 @@ struct rpc_clnt {
 
 	int			cl_nodelen;	/* nodename length */
 	char 			cl_nodename[UNX_MAXNODENAME];
-	char			cl_pathname[30];/* Path in rpc_pipe_fs */
 	struct path		cl_path;
 	struct rpc_clnt *	cl_parent;	/* Points to parent of clones */
 	struct rpc_rtt		cl_rtt_default;