dt-bindings: mfd: cirrus,cs42l43: Add initial DT binding

dt-bindings: mfd: cirrus,cs42l43: Add initial DT binding

The CS42L43 is an audio CODEC with integrated MIPI SoundWire interface
(Version 1.2.1 compliant), I2C, SPI, and I2S/TDM interfaces designed
for portable applications. It provides a high dynamic range, stereo
DAC for headphone output, two integrated Class D amplifiers for
loudspeakers, and two ADCs for wired headset microphone input or
stereo line input. PDM inputs are provided for digital microphones.

Add a YAML DT binding document for this device.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230804104602.395892-3-ckeepax@opensource.cirrus.com
Signed-off-by: Lee Jones <lee@kernel.org>