SUNRPC: display human-readable procedure name in rpc_iostats output

Add fields to the rpc_procinfo struct that allow the display of a
human-readable name for each procedure in the rpc_iostats output.

Also fix it so that the NFSv4 stats are broken up correctly by
sub-procedure number.  NFSv4 uses only two real RPC procedures:
NULL, and COMPOUND.

Test plan:
Mount with NFSv2, NFSv3, and NFSv4, and do "cat /proc/self/mountstats".

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

include/linux/sunrpc/clnt.h

@@ -101,6 +101,8 @@ struct rpc_procinfo {
 	unsigned int		p_bufsiz;	/* req. buffer size */
 	unsigned int		p_count;	/* call count */
 	unsigned int		p_timer;	/* Which RTT timer to use */
+	u32			p_statidx;	/* Which procedure to account */
+	char *			p_name;		/* name of procedure */
 };
 
 #define RPC_CONGESTED(clnt)	(RPCXPRT_CONGESTED((clnt)->cl_xprt))