实现多字节的十六制数的相乘，入口为被乘数高字节地址，乘数高字节地址，字节数，出口为积最高字节地址-The realization of multi-byte number of the system multiplied by 16, the entrance of the high-byte address for the multiplicand, the multiplier high byte address, byte count, exports the highest byte address for the plot