clk: tegra: pll: Add specialized logic for Tegra210

On Tegra210 SoC's, the logic to enable several of the plls is different
from previous generations. Therefore, add registration functions specific
to Tegra210 which will handle them appropriately.

Reviewed-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>