dt-bindings: clock: tegra: Document Tegra132 compatible

The Tegra132 clock and reset controller is largely compatible with the
version found on Tegra124 but it does have slight differences in what
clocks it exposes, so a separate compatible string is needed.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>