tegra: medcom: Add device tree support

Device tree support is required for working USB host support, which in
turn enables ethernet support.

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