For certain special cases, RPC-related tracepoints record a -1 as
the task ID or the client ID. It's ugly for a trace event to display
4 billion in these cases.

To help keep SUNRPC tracepoints consistent, create a macro that
defines the print format specifiers for tk_pid and cl_clid. At some
point in the future we might try tk_pid with a wider range of values
than 0..64K so this makes it easier to make that change.

RPC tracepoints now look like this:

<...>-1276  [009]   149.720358: rpc_clnt_new:         client=00000005 peer=[192.168.2.55]:20049 program=nfs server=klimt.ib

<...>-1342  [004]   149.921234: rpc_xdr_recvfrom:     task:0000001a@00000005 head=[0xff1242d9ab6dc01c,144] page=0 tail=[(nil),0] len=144
<...>-1342  [004]   149.921235: xprt_release_cong:    task:0000001a@00000005 snd_task:ffffffff cong=256 cwnd=16384
<...>-1342  [004]   149.921235: xprt_put_cong:        task:0000001a@00000005 snd_task:ffffffff cong=0 cwnd=16384
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>