dt-bindings: clock: Add SM8250 GCC clock bindings

Add device tree bindings for global clock controller on SM8250 SoCs.

Signed-off-by: Taniya Das <tdas@codeaurora.org>
Signed-off-by: Venkata Narendra Kumar Gutta <vnkgutta@codeaurora.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Link: https://lkml.kernel.org/r/20200224045003.3783838-5-vkoul@kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>