[nrf fromlist] boards: nrf54h0: iron: enable cpusec_bellboard for cpuapp

Upstream PR #: 89333

Enable the cpusec_bellboard by default for the cpuapp iron board variant
so that IPC toward the secure domain is available by default. Because
IPC is needed to boot the radio core, this fits the standard use case.

Signed-off-by: Jonathan Nilsen <[email protected]>
(cherry picked from commit e09a30c)

Author: jonathannilsen

boards/nordic/nrf54h20dk/nrf54h20dk_nrf54h20_cpuapp_iron.dts

@@ -17,6 +17,10 @@
 	};
 };
 
+&cpusec_bellboard {
+	status = "okay";
+};
+
 &cpusec_cpuapp_ipc {
 	mbox-names = "tx", "rx";
 	status = "okay";