dt-bindings: display/msm: gpu: Document A612 GPU

dt-bindings: display/msm: gpu: Document A612 GPU

A612 GPU has a new IP called RGMU (Reduced Graphics Management Unit)
which replaces GMU. But it doesn't do clock or voltage scaling. So we
need the gpu core clock in the GPU node along with the power domain to
do clock and voltage scaling from the kernel. Update the bindings to
describe this GPU.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Akhil P Oommen <akhilpo@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/696676/
Message-ID: <20251231-qcs615-spin-2-v6-3-da87debf6883@oss.qualcomm.com>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>