Add guards for mbedtls_psa_crypto_free()

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/programs/x509/load_roots.c b/programs/x509/load_roots.c
index bca6e88..e28f35a 100644
--- a/programs/x509/load_roots.c
+++ b/programs/x509/load_roots.c
@@ -200,7 +200,9 @@
     exit_code = MBEDTLS_EXIT_SUCCESS;
 
 exit:
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
     mbedtls_psa_crypto_free();
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
     mbedtls_exit(exit_code);
 }
 #endif /* necessary configuration */