bpf: fix cbpf parser bug for octal numbers

Range is 0-7, not 0-9, otherwise parser silently excludes it from the
strtol() rather than throwing an error.

Reported-by: Marc Boschma <marc@boschma.cx>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>