xprtrdma: Clean up trace_xprtrdma_post_linv

- Replace the display of kernel memory addresses
- Add "_err" to the end of its name to indicate that it's a
  tracepoint that fires only when there's an error

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