zephyr: boards: nrf54h20dk: disable power domains

The nrf54h20 power domains are forced on at boot, no need to
enable them or their drivers unless they are to be managed further
within the bootloader.

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>

Author: bjarki-andreasen

boot/zephyr/boards/nrf54h20dk_nrf54h20_cpuapp_iron.conf

@@ -8,4 +8,6 @@ CONFIG_SPI_NOR=n
 
 CONFIG_BOOT_WATCHDOG_FEED=n
 
-CONFIG_MULTITHREADING=y
+# Power domains forced on by default on boot, no need
+# to manage them in bootloader.
+CONFIG_POWER_DOMAIN=n

boot/zephyr/boards/nrf54h20dk_nrf54h20_cpuapp_iron.overlay

@@ -0,0 +1,50 @@
+# Copyright (c) 2025 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+&gdpwr {
+	status = "disabled";
+};
+
+&gdpwr_fast_active_0 {
+	status = "disabled";
+};
+
+&gdpwr_fast_active_1 {
+	status = "disabled";
+};
+
+&gdpwr_fast_main {
+	status = "disabled";
+};
+
+&gdpwr_slow_active {
+	status = "disabled";
+};
+
+&gdpwr_slow_main {
+	status = "disabled";
+};
+
+&gpio_pad_group0 {
+	status = "disabled";
+};
+
+&gpio_pad_group1 {
+	status = "disabled";
+};
+
+&gpio_pad_group2 {
+	status = "disabled";
+};
+
+&gpio_pad_group6 {
+	status = "disabled";
+};
+
+&gpio_pad_group7 {
+	status = "disabled";
+};
+
+&gpio_pad_group9 {
+	status = "disabled";
+};