clk: tegra: Reimplement SOR clocks on Tegra210

In order to allow the display driver to deal uniformly with all SOR
generations, implement the SOR clocks in a way that is compatible with
Tegra186 and later.

Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>