MAINTAINERS: Add Actions Semi S900 clk entries

Add S900 clk entries under ARCH_ACTIONS.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>