linux-phytec-fsl

drm/nouveau/tegra: acquire and enable reference clock if needed

GM20B requires an extra clock compared to GK20A. Add that information
into the platform data and acquire and enable this clock if necessary.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>