perf python: Add missing files to binding link list

Fixing this problem, introduced recently:

  $ perf test python
  16: Try 'import perf' in python, checking link problems      : FAILED!

In verbose mode we find out what is missing:

  $ perf test -v python
  16: Try 'import perf' in python, checking link problems      :
  --- start ---
  test child forked, pid 24894
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  ImportError: /tmp/build/perf/python/perf.so: undefined symbol: find_next_bit
  test child finished with -1
  ---- end ----
  Try 'import perf' in python, checking link problems: FAILED!
  $

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: f77b57ad ("perf cpu_map: Add cpu_map__new_event function")
Link: http://lkml.kernel.org/n/tip-rajx0zkz6czdrnvvwf0jp76p@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/python-ext-sources

@@ -10,6 +10,8 @@ util/ctype.c
 util/evlist.c
 util/evsel.c
 util/cpumap.c
+util/bitmap.c
+../lib/util/find_next_bit.c
 ../lib/hweight.c
 util/thread_map.c
 util/util.c