dt-bindings: Add Tegra234 MGBE clocks and resets

Add the clocks and resets used by the MGBE Ethernet hardware found on
Tegra234 SoCs.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Bhadram Varka <vbhadram@nvidia.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>