ARM: mxs: add support for I2SE Duckbill 2 boards

The Duckbill devices are small, pen-drive sized boards based on
NXP's i.MX28 SoC. While the initial variants (Duckbill series)
were equipped with a micro SD card slot only, the latest generation
(Duckbill 2 series) have an additional internal eMMC onboard.

To distinguish between both generations, a new device tree
compatible string was introduced. To get the MAC address fixup
applied, we need to check for this new string here, too.

Signed-off-by: Michael Heimpold <michael.heimpold@i2se.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>