arm64: dts: Add Adreno GPU definitions

Add an initial node for the Adreno GPU.

Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Andy Gross <agross@kernel.org>