clk: hi6220: add acpu clock

Add acpu clock, including sft clock controlling hi6220 coresight module

Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Li Pengcheng <lipengcheng8@huawei.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>