tools/bpftool: Relicense bpftool's BPF profiler prog as dual-license GPL/BSD

Relicense it to be compatible with the rest of bpftool files.

Suggested-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200619222024.519774-1-andriin@fb.com