ASoC: dt-bindings: sama7g5-pdmc: add microchip,startup-delay-us binding

PDMC can work with different types of microphones, thus different boards
could have different microphones. Depending on microphone type the PDMC
would need to wait longer or shorter period (at startup) than the default
chosen one to filter unwanted noise. Thus add microchip,startup-delay-us
binding to let PDMC users to specify startup delay.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230228110145.3770525-3-claudiu.beznea@microchip.com


Signed-off-by: Mark Brown <broonie@kernel.org>