clk: rockchip: add sclk_timer5 as critical clock on rk3128

sclk_timer5 is for arm arch counter, so need always on.
but no dts node to handle this clk, so make it as critical clock

Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>