samples: tfm_integration: adapt DTS overlays for STM32L562 board

Due to changes in flash_layout.h for STM32L562, in the current
TF-M module update, we need to modify the DTS overlay files in
the TF-M samples where the board is supported.

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