board: asus: transformer: add ASUS Transformer T20 family support

The Asus Eee Pad Transformer family are 2-in-1 detachable/slider
tablets developed by Asus that run the Android operating system.
The Eee Pad Transformers feature a 10.1-inch (260 mm) display,
an Nvidia Tegra 2 dual-core chip, 1 GB of RAM, and 16/32 GB of storage.
Transformers board derives from Nvidia Ventana development board.

This patch brings support for all 3 known T20 Transformers:
- Asus Eee Pad Transformer TF101
- Asus Eee Pad Transformer TF101G
- Asus Eee Pad Slider SL101

Tested-by: Robert Eckelmann <longnoserob@gmail.com> # ASUS TF101
Tested-by: Antoni Aloy Torrens <aaloytorrens@gmail.com> # ASUS TF101
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>

include/configs/transformer-t20.h

@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  (C) Copyright 2010,2011
+ *  NVIDIA Corporation <www.nvidia.com>
+ *
+ *  (C) Copyright 2022
+ *  Svyatoslav Ryhel <clamor95@gmail.com>
+ */
+
+#ifndef __CONFIG_H
+#define __CONFIG_H
+
+#include "tegra20-common.h"
+#include "transformer-common.h"
+
+/* Board-specific serial config */
+#define CFG_SYS_NS16550_COM1		NV_PA_APB_UARTD_BASE
+
+#include "tegra-common-post.h"
+
+#endif /* __CONFIG_H */