tegra: add Colibri T20 board support

This adds board support for the Toradex Colibri T20 module.

Working functions:
- SD card boot
- USB boot
- Network
- NAND environment

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 1b2da94..5a500c5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -902,6 +902,10 @@
 
 	zynq		ARM ARMV7 (Zynq SoC)
 
+Lucas Stach <dev@lynxeye.de>
+
+	colibri_t20_iris	Tegra20 (ARM7 & A9 Dual Core)
+
 Nick Thompson <nick.thompson@gefanuc.com>
 
 	da830evm	ARM926EJS (DA830/OMAP-L137)