GPIO: don't turn off on boot

[xarantolus]

Before this, #82 turned off the LED on boot. Now it takes the default-state value:

leds: leds {
  compatible = "gpio-leds";
  
  green_led_0: led_0 {
	  gpios = <&gpioc 7 GPIO_ACTIVE_HIGH>;
	  label = "User LD1";
	  default-state = "on";
  };
}

[thomasw04]

Looks good to me.

[Copilot]

Pull request overview

This PR updates the gpio-leds pipeline (device-tree codegen → HAL registry → kernel LED driver init) so LEDs no longer get forced off during boot, and instead honor the DTS default-state property (e.g., "on").

Changes:

• Extend dtgen gpio-leds codegen to parse default-state and emit it in LedRegistryEntry.
• Add a LedDefaultState enum to the generated device-tree API and the host/test stub API.
• Update the kernel LED driver to set the initial output level based on default-state (including a best-effort keep behavior).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
xtasks/crates/dtgen/src/codegen/led.rs	Parse default-state from DT and emit LedDefaultState + default_state in the registry entries.
src/drivers/led.rs	Initialize GPIO output level according to the generated default_state value and log it.
machine/cortex-m/src/stub/device_tree.rs	Mirror the new LedDefaultState/default_state API in the stub device tree for host/test builds.

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