drm/tegra: add MODULE_DEVICE_TABLEs

When tegra-drm.ko is built as a module, these MODULE_DEVICE_TABLEs allow
the module to be auto-loaded since the module will match the devices
instantiated from device tree.

(Notes for stable: in 3.14+, just git rm any conflicting file, since they
are added in later kernels. For 3.13 and below, manual merging will be
needed)

Cc: <stable@vger.kernel.org>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>