perf MANIFEST: Add bpftool files to allow building with BUILD_BPF_SKEL=1

We need bpftool and required kernel/bpf/disasm.[ch] to bootstrap the
cgroups, bperf and other BPF skels used by perf.

Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/MANIFEST

···
 tools/lib/vsprintf.c
 tools/lib/zalloc.c
 scripts/bpf_doc.py
+tools/bpf/bpftool
+kernel/bpf/disasm.c
+kernel/bpf/disasm.h