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>
diff --git a/board/asus/transformer-t20/configs/tf101g.config b/board/asus/transformer-t20/configs/tf101g.config
new file mode 100644
index 0000000..0ccf249
--- /dev/null
+++ b/board/asus/transformer-t20/configs/tf101g.config
@@ -0,0 +1 @@
+CONFIG_DEFAULT_DEVICE_TREE="tegra20-asus-tf101g"