perf tools: Simplify event_read_id exit path

We're freeing the token in any case so simplify the exit path by
unifying it.

No functional change.

Signed-off-by: Borislav Petkov <bp@amd64.org>
Link: http://lkml.kernel.org/r/1332339347-21342-1-git-send-email-bp@amd64.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>