ASoC: Add generic RPI driver for simple soundcards.

ASoC: Add generic RPI driver for simple soundcards.

The RPI simple sound card driver provides a generic ALSA SOC card driver
supporting a variety of Pi HAT soundcards. The intention is to avoid
the duplication of code for cards that can't be fully supported by
the soc simple/graph cards but are otherwise almost identical.

This initial commit adds support for the ADAU1977 ADC, Google VoiceHat,
HifiBerry AMP, HifiBerry DAC and RPI DAC.

Signed-off-by: Tim Gover <tim.gover@raspberrypi.org>
ASoC: Use correct card name in rpi-simple driver

Use the specific card name from drvdata instead of the snd_rpi_simple

rpi-simple-soundcard: Use nicer driver name "RPi-simple"

Rename the driver from "RPI simple soundcard" to "RPi-simple" so that
the driver name won't be mangled allowing to be used unaltered as the
card conf filename.