ASoC: hifiberry_dacplusadc: fix DAI link setup

The driver only defines a single DAI link and the code that tries
to setup the second (non-existent) DAI link looks wrong - using dmic
as a CPU/platform driver doesn't make any sense.

The DT overlay doesn't define a dmic property, so the code was never
executed (otherwise it would have resulted in a memory corruption).

So drop the offending code to prevent issues if a dmic property
should be added to the DT overlay.

Signed-off-by: Matthias Reichl <hias@horus.com>