arm64: dts: qcom: use sm8250 gpucc dt-bindings

Constants were used to allow merging separately from the dt-bindings,
switch to symbolic names now that dt-bindings have landed.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Link: https://lore.kernel.org/r/20200818160445.14008-3-jonathan@marek.ca


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