ARM: tegra: add missing clock documentation to DT bindings

Many of the Tegra DT binding documents say nothing about the clocks or
clock-names properties, yet those are present and required in DT files.
This patch simply updates the documentation file to match the implicit
definition of the binding, based on real-world DT content.

All Tegra bindings that mention clocks are updated to have consistent
wording and formatting of the clock-related properties.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-By: Terje Bergstrom <tbergstrom@nvidia.com>