[nrf noup] boards: arm: nrf9131ek: enable tfm

This patch backports the nrf9131ek to a time before tfm was refactored.

To be reverted when TF-M is updated.

Signed-off-by: Maximilian Deubel <[email protected]>
(cherry picked from commit ca2646b)

Author: maxd-nordic

boards/nordic/nrf9131ek/Kconfig.defconfig

@@ -8,3 +8,22 @@ config HW_STACK_PROTECTION
 
 config BOARD_NRF9131EK
 	select USE_DT_CODE_PARTITION if BOARD_NRF9131EK_NRF9131_NS
+
+if BOARD_NRF9131EK_NRF9131 || BOARD_NRF9131EK_NRF9131_NS
+
+# By default, if we build for a Non-Secure version of the board,
+# enable building with TF-M as the Secure Execution Environment.
+config BUILD_WITH_TFM
+	default y if BOARD_NRF9131EK_NRF9131_NS
+
+if BUILD_WITH_TFM
+
+# By default, if we build with TF-M, instruct build system to
+# flash the combined TF-M (Secure) & Zephyr (Non Secure) image
+config TFM_FLASH_MERGED_BINARY
+	bool
+	default y
+
+endif # BUILD_WITH_TFM
+
+endif # BOARD_NRF9131EK_NRF9131 || BOARD_NRF9131EK_NRF9131_NS