ASoC: atmel: mchp-pdmc: add PDMC driver

The Pulse Density Microphone Controller (PDMC) interfaces up to 4 digital
microphones having Pulse Density Modulated (PDM) outputs. It generates a
single clock line and samples 1 or 2 data lines. The signal path includes
an audio grade programmable decimation filter and outputs 24-bit audio
words on the APB bus.

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Link: https://lore.kernel.org/r/20220307122202.2251639-4-codrin.ciubotariu@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>