Returns list of changed ports.
iex> Numato.Utils.get_changed_ports(<<0xFF>>, <<0xFE>>, <<0xFF>>) [{0, 0}]
iex> Numato.Utils.get_changed_ports(<<0xFC>>, <<0xFF>>, <<0xFF>>) [{0, 1}, {1, 1}]
iex> Numato.Utils.get_changed_ports(<<0xFC>>, <<0xFF>>, <<0x01>>) [{0, 1}]