perf tools: Add missing sources to perf's MANIFEST

Adding missing bitmap.[ch] sources to the MANIFEST file. Fixes building
'make perf-*-src-pkg' generated tarballs.

Reported-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Fixes: 915b0882 ("tools lib: Move bitmap.[ch] from tools/perf/ to tools/{lib,include}/")
Link: http://lkml.kernel.org/r/1452509693-13452-5-git-send-email-jolsa@kernel.org


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