clk: imx: scu: Only save DC SS clock using non-cached clock rate

Display sub-system has special clock settings in SCFW, the
bypassed clock is used instead of PLL in Linux kernel clock
tree, so when saving clock rate, need to save non-cached clock
rate for Display sub-system's bypass clocks, and other clocks
still use the cached clock rate which is with runtime PM ON.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>