dt-bindings: dma: nvidia,tegra20-apbdma: convert text based binding to json schema

dt-bindings: dma: nvidia,tegra20-apbdma: convert text based binding to json schema

Update text binding to YAML.
Changes during conversion:
- Add a fallback for "nvidia,tegra30-apbdma" as it is
  compatible with the IP core on "nvidia,tegra20-apbdma".
- Update examples and include appropriate file directives to resolve
  errors identified by `dt_binding_check` and `dtbs_check`.

Signed-off-by: Charan Pedumuru <charan.pedumuru@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250507-nvidea-dma-v4-2-6161a8de376f@gmail.com
Signed-off-by: Thierry Reding <treding@nvidia.com>