clk: hisilicon: Add clock driver for hi3660 SoC

Add clock drivers for hi3660 SoC, this driver controls the SoC
registers to supply different clocks to different IPs in the SoC.

Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
[sboyd@codeaurora.org: Simplify probe with function pointer]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>