dt-bindings: clock: Introduce SC7180 QCOM Graphics clock bindings

Add device tree bindings for graphics clock controller for
Qualcomm Technology Inc's SC7180 SoCs.

Signed-off-by: Taniya Das <tdas@codeaurora.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lkml.kernel.org/r/1577428714-17766-3-git-send-email-tdas@codeaurora.org


[sboyd@kernel.org: Indicate sc7180 in commit subject]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>