Adapt remaining guards to FFDH

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index bee86ca..00036e1 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -4214,12 +4214,13 @@
     mbedtls_ssl_buffering_free(ssl);
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
-#if defined(PSA_WANT_ALG_ECDH) && \
+#if (defined(PSA_WANT_ALG_ECDH) || defined(PSA_WANT_ALG_FFDH)) && \
     (defined(MBEDTLS_USE_PSA_CRYPTO) || defined(MBEDTLS_SSL_PROTO_TLS1_3))
     if (handshake->ecdh_psa_privkey_is_external == 0) {
         psa_destroy_key(handshake->ecdh_psa_privkey);
     }
-#endif /* PSA_WANT_ALG_ECDH && (MBEDTLS_USE_PSA_CRYPTO || MBEDTLS_SSL_PROTO_TLS1_3) */
+#endif /* (PSA_WANT_ALG_ECDH || PSA_WANT_ALG_FFDH) &&
+          (MBEDTLS_USE_PSA_CRYPTO || MBEDTLS_SSL_PROTO_TLS1_3) */
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3)
     mbedtls_ssl_transform_free(handshake->transform_handshake);