perf python: Add missing perf_event__parse_sample 'swapped' parm

Problem introduced in 936be503

, that missed one perf_event__parse_sample
user, the python binding.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.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-ja4phms9618ggi657plyuch2@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>