Added support for HiFiBerry DAC+

The driver is based on the HiFiBerry DAC driver. However HiFiBerry DAC+ uses
a different codec chip (PCM5122), therefore a new driver is necessary.
ASoC: BCM: Typo in RPi-DAC driver

This patch corrects a typo that originated from
inattentive copy and paste.

Signed-off-by: Florian Meier <florian.meier@koalo.de>