The PSA external RNG does not require MBEDTLS_USE_PSA_CRYPTO

The dependency is on MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG plus
MBEDTLS_PSA_CRYPTO_C. MBEDTLS_USE_PSA_CRYPTO is irrelevant.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/include/test/helpers.h b/tests/include/test/helpers.h
index ce8a1e2..9da2cdb 100644
--- a/tests/include/test/helpers.h
+++ b/tests/include/test/helpers.h
@@ -190,7 +190,7 @@
 void mbedtls_test_param_failed_reset_state( void );
 #endif /* MBEDTLS_CHECK_PARAMS */
 
-#if defined(MBEDTLS_USE_PSA_CRYPTO) && defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
+#if defined(MBEDTLS_PSA_CRYPTO_C) && defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
 #include "test/fake_external_rng_for_test.h"
 #endif