Tegra: Medcom-Wide: Enable NAND and boot script support

Boot script support brings Medcom-Wide in line with other Tegra boards.
In order to enable booting a Linux kernel with initial ramdisk, also add
support for the new FIT image type.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Tom Warren <twarren@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>