samples: tfm_ipc: update DT overlay for nucleo_l552ze_q_ns

Update overlay file for nucleo_l552ze_q_ns board,
since now the sample does not enable REGRESSION,
and thus regular TF-M flash layout for the board
is used.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2 files changed