ARM: tegra: define Tegra30 CAR binding

The device tree binding models Tegra30 CAR (Clock And Reset)
as a single monolithic clock provider.

Signed-off-by: Prashant Gaikwad <pgaikwad@nvidia.com>
[swarren: fixed typo in binding doc]
Signed-off-by: Stephen Warren <swarren@nvidia.com>