dt-bindings: tegra: pmc: Update aotag as an optional aperture

dt-bindings: tegra: pmc: Update aotag as an optional aperture

Not all Tegra SoCs or all versions of a particular Tegra SoC may include
the AOTAG aperture. This change makes "aotag" as an optional aperture for
Tegra234 and Tegra264.

Co-developed-by: Prathamesh Shete <pshete@nvidia.com>
Signed-off-by: Prathamesh Shete <pshete@nvidia.com>
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>