clk: actions: Add clock driver for S500 SoC

Add common clock driver for Actions Semi S500 SoC.

Signed-off-by: Edgar Bernardi Righi <edgar.righi@lsitec.org.br>
[Mani: cleaned up the driver]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>