[nrf fromlist] boards: nrf54h20: iron: keep cpusec_cpuapp_ipc

Support IPC between SEC and APP. This is needed for PSA Crypto
support.

Upstream PR #: 88285

Ref: NCSDK-NONE

Signed-off-by: Sebastian Bøe <[email protected]>

Author: SebastianBoe

boards/nordic/nrf54h20dk/nrf54h20dk_nrf54h20_cpuapp_iron.dts

@@ -8,7 +8,6 @@
 
 /delete-node/&cpurad_rx_partitions;
 /delete-node/&cpuapp_rx_partitions;
-/delete-node/&cpusec_cpuapp_ipc;
 
 /* This is not yet an exhaustive memory map, and contain only a minimum required to boot
  * the application core.