Generate DeviceKey Root of Trust if TDB_EXTERNAL is used

TDB_INTERNAL is based on SecureStore which uses DeviceKey.

main.cpp

@@ -20,6 +20,7 @@
 #include <string.h>
 #include "KVStore.h"
 #include "kvstore_global_api.h"
+#include "SecureStore.h"
 
 using namespace mbed;
 
@@ -59,6 +60,11 @@ void kv_store_global_api_example()
     res = kv_reset("/kv/");
     printf("kv_reset -> %d\n", err_code(res));
 
+#if MBED_CONF_STORAGE_STORAGE_TYPE == TDB_EXTERNAL
+    res = DeviceKey::get_instance().generate_root_of_trust();
+    printf("DeviceKey::get_instance().generate_root_of_trust() -> %d\n", res);
+#endif
+
     /* Set First 'Dummy' Key/Value pair with unprotected clear value data */
     printf("kv_set first dummy key\n");
     res = kv_set(kv_key_in, kv_value_in, strlen(kv_value_in), 0);