tls13: keys: Simplify code guard

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/ssl_tls13_keys.c b/library/ssl_tls13_keys.c
index 642b912..ec84a99 100644
--- a/library/ssl_tls13_keys.c
+++ b/library/ssl_tls13_keys.c
@@ -1256,8 +1256,7 @@
     unsigned char *shared_secret = NULL;
     size_t shared_secret_len = 0;
 
-#if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) || \
-    defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL_ENABLED)
+#if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED)
     /*
      * Compute ECDHE secret used to compute the handshake secret from which
      * client_handshake_traffic_secret and server_handshake_traffic_secret
@@ -1311,8 +1310,7 @@
             return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
         }
     }
-#endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED ||
-          MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL_ENABLED */
+#endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_EPHEMERAL_ENABLED */
 
     /*
      * Compute the Handshake Secret