dt-bindings: timestamp: Add Tegra264 support

dt-bindings: timestamp: Add Tegra264 support

Add timestamp provider support for the Tegra264 in devicetree
bindings. Tegra264 has two generic timestamping engines (GTE)
which are the always-on GTE (AON) and legacy interrupt
controller (LIC) GTE.
'nvidia,slices' property is deprecated and hence not allowed for
Tegra264.

Signed-off-by: Suneel Garapati <suneelg@nvidia.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Dipen Patel <dipenp@nvidia.com>