Adapt guards for FFDH

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index e3bc776..fad970c 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -2657,14 +2657,14 @@
     const mbedtls_ssl_ciphersuite_t *suite);
 #endif /* MBEDTLS_SSL_SOME_SUITES_USE_CBC_ETM */
 
-#if defined(PSA_WANT_ALG_ECDH)
+#if defined(PSA_WANT_ALG_ECDH) || defined(PSA_WANT_ALG_FFDH)
 
 MBEDTLS_CHECK_RETURN_CRITICAL
 int mbedtls_ssl_tls13_read_public_ecdhe_share(mbedtls_ssl_context *ssl,
                                               const unsigned char *buf,
                                               size_t buf_len);
 
-#endif /* PSA_WANT_ALG_ECDH */
+#endif /* PSA_WANT_ALG_ECDH || PSA_WANT_ALG_FFDH */
 
 static inline int mbedtls_ssl_tls13_cipher_suite_is_offered(
     mbedtls_ssl_context *ssl, int cipher_suite)