dt-bindings: opp: Add v2-qcom-adreno vendor bindings

Add a new schema which extends opp-v2 to support a new vendor specific
property required for Adreno GPUs found in Qualcomm's SoCs. The new
property called "qcom,opp-acd-level" carries a u32 value recommended
for each opp needs to be shared to GMU during runtime.

Also, update MAINTAINERS file include the new opp-v2-qcom-adreno.yaml.

Cc: Rob Clark <robdclark@gmail.com>
Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Tested-by: Maya Matuszczyk <maccraft123mc@gmail.com>
Tested-by: Anthony Ruhier <aruhier@mailbox.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/649351/


Signed-off-by: Rob Clark <robdclark@chromium.org>