drivers: audio: dmic: add driver for NXP DMIC peripheral

Add driver for NXP DMIC peripheral. This peripheral is present on the
iMX RT5xx and iMX RT6xx parts, as well as some LPC SOCs. The following
features are supported:
- up to 2 simultaneous channels of L/R PCM data (4 channels are not
  supported due to limitations of the DMA engine)
- individual configuration of gain and filter parameters for each DMIC
  channel input

The driver has been tested with up to 4 PCM data streams (2 L/R channels),
as well as the MEMS microphones present on the RT595 EVK.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>
Co-authored-by: Yves Vandervennet <yves.vandervennet@nxp.com>