dts: bindings: clock: rpi_pico: Add default value matching the Pico SDK

The Pico SDK defines a default value for its XOSC multiplier. Reflect
this in the device tree binding so that it doesn't need to be repeated.

Signed-off-by: Andrew Featherstone <[email protected]>

Author: ajf58

dts/bindings/clock/raspberrypi,pico-xosc.yaml

@@ -11,4 +11,6 @@ include: raspberrypi,pico-clock.yaml
 properties:
   startup-delay-multiplier:
     type: int
-    description: Startup delay multiplier
+    default: 1
+    description: |
+      Startup delay multiplier. The default value matches the Pico SDK.