drm/tegra: dc - Compute shift clock divider in output drivers

The shift clock divider is highly dependent on the type of output, so
push computation of it down into the output drivers. The old code used
to work merely by accident.

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

diff --cc drivers/gpu/drm/tegra/dc.c
Simple merge

diff --cc drivers/gpu/drm/tegra/drm.h
Simple merge

diff --cc drivers/gpu/drm/tegra/dsi.c
Simple merge

diff --cc drivers/gpu/drm/tegra/hdmi.c
Simple merge

diff --cc drivers/gpu/drm/tegra/rgb.c
Simple merge

diff --cc drivers/gpu/drm/tegra/sor.c
Simple merge