dt-bindings: clock: Add devicetree binding for BM1880 SoC

Add YAML devicetree binding for Bitmain BM1880 SoC.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lkml.kernel.org/r/20191115162901.17456-4-manivannan.sadhasivam@linaro.org


Signed-off-by: Stephen Boyd <sboyd@kernel.org>