dt-bindings: display/msm/gmu: Add Adreno 663 GMU

Document Adreno 663 GMU in the dt-binding specification.

Signed-off-by: Puranam V G Tejaswi <quic_pvgtejas@quicinc.com>
Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Patchwork: https://patchwork.freedesktop.org/patch/620771/


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