Add support for colibri_t30

This commit adds support for the Toradex Colibri T30 module. Since
we use the same boot loader for all carrier board, in the boot
loader world (U-Boot/BCT) the board name consists of the module
name only, without any reference to the carrier board.

Signed-off-by: Stefan Agner <stefan@agner.ch>
[swarren, disabled board by default until U-Boot supports exists]
Signed-off-by: Stephen Warren <swarren@nvidia.com>