drm/tegra: Bump VIC/NVDEC clock rates to Fmax

To get full performance out of these engines, bump their clock rates
to maximum. In the future we may want something smarter but this
should be fine for now.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>