We only have access to pevent after processing that event, so set the
tracepoint names there.

Right now this isn't a problem as we're deferring resolving the
tracepoint names to when we process samples, but in the next patches we
will be doing it in advance, to avoid relookups, so do it earlier, as
soon as we process the tracing data event.

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: Namhyung Kim <namhyung@gmail.com>
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-tzb7srmsl7a6o3icw592iv2o@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>