[nrf noup] boards: nrf54h20dk: Enable default images for sysbuild

Enable the `empty_app_core` image when building for `cpurad`.

Signed-off-by: Grzegorz Swiderski <[email protected]>
(cherry picked from commit 2ea472d)

Author: 57300

boards/nordic/nrf54h20dk/Kconfig.sysbuild

@@ -0,0 +1,9 @@
+# Copyright (c) 2025 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+if BOARD_NRF54H20DK_NRF54H20_CPURAD
+
+config NRF_DEFAULT_EMPTY
+	default y
+
+endif # BOARD_NRF54H20DK_NRF54H20_CPURAD