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>

Documentation/devicetree/bindings/sound/microchip,sama7g5-pdmc.yaml

@@ -67,6 +67,12 @@ properties:
     maxItems: 4
     uniqueItems: true
 
+  microchip,startup-delay-us:
+    description: |
+      Specifies the delay in microseconds that needs to be applied after
+      enabling the PDMC microphones to avoid unwanted noise due to microphones
+      not being ready.
+
 required:
   - compatible
   - reg