samples|tests: secure-storage: allow all test rng sources

Add MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG_ALLOW_NON_CSPRNG to the list of
test Kconfigs. Typical use case of this:

- the platform has "zephyr,entropy" defined in the devicetree which means
  that CSPRNG_AVAILABLE is set;
- for some reason the board actually does not have any entropy driver
  enabled (ex: ENTROPY_BT_HCI is disabled in nrf5340bsim when BT is _not_
  enabled in the build);
- since TEST_RANDOM_GENERATOR is enabled then also TEST_CSPRNG_GENERATOR
  would be;
- unfortunately the call to psa_generate_random() would fail in
  get_random_data() (in modules/mbedtls/zephyr_entropy.c) because
  MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG_ALLOW_NON_CSPRNG is not set and it would
  not reach "subsys/random/random_test_csprng.c".

This commit fixes this problem.

Signed-off-by: Valerio Setti <vsetti@baylibre.com>

samples/psa/its/overlay-entropy_not_secure.conf

@@ -2,3 +2,4 @@
 
 CONFIG_TEST_RANDOM_GENERATOR=y
 CONFIG_TIMER_RANDOM_GENERATOR=y
+CONFIG_MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG_ALLOW_NON_CSPRNG=y

samples/psa/persistent_key/overlay-entropy_not_secure.conf

@@ -2,3 +2,4 @@
 
 CONFIG_TEST_RANDOM_GENERATOR=y
 CONFIG_TIMER_RANDOM_GENERATOR=y
+CONFIG_MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG_ALLOW_NON_CSPRNG=y

tests/subsys/secure_storage/psa/crypto/overlay-secure_storage.conf

@@ -4,6 +4,7 @@ CONFIG_MAIN_STACK_SIZE=2048
 CONFIG_MBEDTLS=y
 CONFIG_TEST_RANDOM_GENERATOR=y
 CONFIG_TIMER_RANDOM_GENERATOR=y
+CONFIG_MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG_ALLOW_NON_CSPRNG=y
 # PSA Crypto needs some heap, but MINIMAL_LIBC has none by default.
 CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE=2048
 CONFIG_MBEDTLS_PSA_CRYPTO_C=y

tests/subsys/secure_storage/psa/its/overlay-transform_default.conf

@@ -1,6 +1,7 @@
 CONFIG_MBEDTLS=y
 CONFIG_TEST_RANDOM_GENERATOR=y
 CONFIG_TIMER_RANDOM_GENERATOR=y
+CONFIG_MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG_ALLOW_NON_CSPRNG=y
 # PSA Crypto needs some heap, but MINIMAL_LIBC has none by default.
 CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE=2048
 CONFIG_MBEDTLS_PSA_CRYPTO_C=y