colibri/apalis tegra: drop DFU support

We never really added a sensible DFU configuration for platforms
based on eMMC. Most of the things one might want to do can also be done
with UMS or fastboot, so drop the DFU configuration.

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Reviewed-by: Philippe Schenker <philippe.schenker@toradex.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>