reset: implement a driver for the Tegra CAR

Implement a reset uclass driver for the Tegra CAR. This allows clients to
use standard reset APIs on Tegra. This device is intended to be
instantiated by the core Tegra CAR driver, rather than being instantiated
directly from DT. The implementation uses the existing custom Tegra-
specific reset APIs to avoid coupling the series with significant
refactoring of the existing Tegra clock/reset code.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>