clk: hisilicon: Add clock driver for Hi3670 SoC

Add clock driver for HiSilicon Hi3670 SoC utilizing HiSilicon's
common clk code.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>