Use ecdh_setup instead of ecp_group_load

Align files with development to ensure the same state of repositories.
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 6f7a9aa..8a90288 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -3088,8 +3088,8 @@
 
         MBEDTLS_SSL_DEBUG_MSG( 2, ( "ECDHE curve: %s", (*curve)->name ) );
 
-        if( ( ret = mbedtls_ecp_group_load( &ssl->handshake->ecdh_ctx.grp,
-                                       (*curve)->grp_id ) ) != 0 )
+        if( ( ret = mbedtls_ecdh_setup( &ssl->handshake->ecdh_ctx,
+                                        (*curve)->grp_id ) ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecp_group_load", ret );
             return( ret );