Build: Update to IAR support

Cleaned up #ifdef in secure_fw/services/tfm_spm_db.inc.template
Moved "signals" member to front of spm_partition_runtime_data_t.
The suggestion to move the aggregate types to the front turned
out to be hard to make work for both PSA and non-PSA configs.

Moved REGION_DECLARE macros to new include file,
platform/include/region.h.

Cleaned up type cast in core_test_api.c

Change-Id: I5dce1e7c019d4d7e4c14dc79be5ee2b855ad4f9e
Signed-off-by: Thomas Tornblom <thomas.tornblom@iar.com>
diff --git a/bl2/ext/mcuboot/flash_map_extended.c b/bl2/ext/mcuboot/flash_map_extended.c
index 887f89b..f84d698 100644
--- a/bl2/ext/mcuboot/flash_map_extended.c
+++ b/bl2/ext/mcuboot/flash_map_extended.c
@@ -28,7 +28,7 @@
     if (fd_id != FLASH_DEVICE_ID) {
         BOOT_LOG_ERR("invalid flash ID %d; expected %d",
                      fd_id, FLASH_DEVICE_ID);
-        return -EINVAL;
+        return -1;
     }
     *ret = FLASH_DEVICE_BASE;
     return 0;
@@ -47,7 +47,7 @@
     case 2: return FLASH_AREA_IMAGE_SCRATCH;
     }
 
-    return -EINVAL; /* flash_area_open will fail on that */
+    return -1; /* flash_area_open will fail on that */
 }
 
 int flash_area_id_from_image_slot(int slot)