If this port is a bus, it describes the endian-ness of
how the bits in the bus vector are arranged. If the bus is
little endian, LSB (least significant bit) is the rightmost bit
(bus[7:0]). If the bus is not little endian (big endian), LSB is the
left most bit (bus[0:7]).
True if this bus is little endian, false otherwise. Not
applicable for single bit ports.