boards: nrf54h20pdk: Add default IPC configuration

Add `zephyr,ipc-icmsg*` nodes, with mboxes specified in a common file.

Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>
Signed-off-by: Gerard Marull-Partetas <gerard@teslabs.com>
4 files changed