library: add remaining changes for the new ECP_LIGHT symbol

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/ssl_client.c b/library/ssl_client.c
index eb52e70..e84c28a 100644
--- a/library/ssl_client.c
+++ b/library/ssl_client.c
@@ -257,7 +257,7 @@
     for (; *group_list != 0; group_list++) {
         MBEDTLS_SSL_DEBUG_MSG(1, ("got supported group(%04x)", *group_list));
 
-#if defined(MBEDTLS_ECP_C)
+#if defined(MBEDTLS_ECP_LIGHT)
         if ((mbedtls_ssl_conf_is_tls13_enabled(ssl->conf) &&
              mbedtls_ssl_tls13_named_group_is_ecdhe(*group_list)) ||
             (mbedtls_ssl_conf_is_tls12_enabled(ssl->conf) &&
@@ -273,7 +273,7 @@
                                       mbedtls_ssl_get_curve_name_from_tls_id(*group_list),
                                       *group_list));
         }
-#endif /* MBEDTLS_ECP_C */
+#endif /* MBEDTLS_ECP_LIGHT */
         /* Add DHE groups here */
 
     }