bpf: Sync bpf.h uapi to tools/

This patch sync include/uapi/linux/bpf.h to
tools/include/uapi/linux/

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>