perf test: Clarify the "sample parsing" test entry

perf test: Clarify the "sample parsing" test entry

Before:

  [root@sandy ~]# perf test -v 22
  22: Test sample parsing                                    :
  --- start ---
  sample format has changed - test needs updating
  ---- end ----
  Test sample parsing: FAILED!
  [root@sandy ~]#

After:

  [root@sandy ~]# perf test -v 22
  22: Test sample parsing                                    :
  --- start ---
  sample format has changed, some new PERF_SAMPLE_ bit was introduced - test needs updating
  ---- end ----
  Test sample parsing: FAILED!
  [root@sandy ~]#

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-8cazc2fpmk70jcbww8c0cobx@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>