The Realtek ALC88 is a chip used on the carrier boards Daisy and Lily. It is a HDA codec which provides several audio output and input signals on a carrier board. The ALC888 is connected to the HDA interface of the CoM Express connector.
This driver is only required if the ALC888 from Realtek is assembled on the carrier board, for example on Lily or Daisy. If you are using a carrier board without the ALC888, this driver doesn't need to be installed.