drm/tegra: Allow the driver to be built as a module
drm/tegra: Allow the driver to be built as a module

All APIs that the driver uses are exported, so the driver can now be
built as a module.

Signed-off-by: Thierry Reding <3055038c414aef68bf32c33b8118623e7554e0f2@nvidia.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs