arm64: dts: qcom: msm8996: Add gpu cooling support

Add cooling-cells property and cooling maps for the GPU.

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
Link: https://lore.kernel.org/r/Ku7mRZ_q2mYDZQ048IPlAc8VOVhH8N4uENhMI-JXxjeiZxjbRRs40ZJYwREb_ScgCvtQgtdl1VRjoDd7CR_8vCrbWVe8n3MwyB1S3VbSDis=@protonmail.com


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>