perf tools: Add include/err.h into MANIFEST

perf tools: Add include/err.h into MANIFEST

Otherwise the tarpkg is incomplete (tarpkg tests fails).

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>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 01ca9fd41d6f ("tools: Add err.h with ERR_PTR PTR_ERR interface")
Link: http://lkml.kernel.org/r/1442846143-8556-1-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>