烧写外部FLASH程序

代码说明：

  将小文件写入外部SPI FLASH中，现将文件写入到单片机的某块flash区域，然后在写入外部falsh，适合小文件(Write the small file to the external SPI FLASH, now write the file to a single chip flash area of the single chip, and then write the external falsh to suit the small file.)