ASOc: Add HiFiBerry DAC8X to the simple card driver

Defines the settings for the 8 channel version of the standard
DAC by overwriting the number of channels in the DAI defs.
It can run in 8ch mode only on PI5 using the 4 lane data output
of the designware I2S0 module.

Signed-off-by: j-schambacher <joerg@hifiberry.com>