clk: tegra: Fix Tegra210 PLLU initialization

- Added necessary delays in PLLU enable sequence during initialization
- Applied PLLU lock to all secondary gates (PLLU_48M and PLLU_60M were
missing).

Signed-off-by: Alex Frid <afrid@nvidia.com>
Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>