ARM: dts: add support for I2SE Duckbill 2 boards

This machine is an USB pen drive sized development board,
based on NXP's i.MX28 CPU. In contrast to the previous
model "Duckbill", the "Duckbill 2" series has internal
eMMC storage.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>
Cc: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>