tools lib bpf: Define prog_type fns with macro

Turning this into a macro allows future prog types to be added with a
single line per type.

Signed-off-by: Joe Stringer <joe@ovn.org>
Acked-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/20170123011128.26534-3-joe@ovn.org


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