perf session: Fix indent in perf_session__new()"

Fix up indentation.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: http://lore.kernel.org/lkml/20191007112027.GD6919@kravaSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>