perf session: Fix undeclared 'oe'

Using linux-3.18.y branch, perf build fails with the following:

    $ make -s -j16 -C tools/perf V=1 WERROR=0 NO_LIBUNWIND=1 HAVE_CPLUS_DEMANGLE=1 NO_GTK2=1 NO_LIBNUMA=1 NO_STRLCPY=1 NO_BIONIC=1 prefix=/usr DESTDIR=/tmp/builddir/build all
    [...]
    util/session.c: In function ‘__perf_session__process_pipe_events’:
    util/session.c:1093:36: error: ‘oe’ undeclared (first use in this function)
      ordered_events__set_copy_on_queue(oe, true);
                                        ^
    util/session.c:1093:36: note: each undeclared identifier is reported only once for each function it appears in

This patch fixes it for linux-3.18.y branch.

---
Hi, Greg.

Perf build on linux-3.18.y is broken since v3.18.101 (v3.18.100 worked just fine). This fixes it.

Changes since v2:
- rebased on v3.18.108

 tools/perf/util/session.c | 1 +
 1 file changed, 1 insertion(+)

index dc3d3b1b813e..c2d4a7ec40df 100644
@@ -1073,6 +1073,7 @@ volatile int session_done;
 static int __perf_session__process_pipe_events(struct perf_session *session,
 					       struct perf_tool *tool)
 {
+	struct ordered_events *oe = &session->ordered_events;
 	int fd = perf_data_file__fd(session->file);
 	union perf_event *event;
 	uint32_t size, cur_size = 0;

2.14.3