Add VIA support for dm9records/tartan (#11666)

keyboards/dm9records/tartan/keymaps/via/config.h

@@ -0,0 +1,23 @@
+/* Copyright 2021 padfoot
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#define DYNAMIC_KEYMAP_LAYER_COUNT 6
+
+/* This is 4 by default. ATMEGA328P's memory doesn't seem to be able to
+ * support more than 6 dynamic keymap layers
+ */