clk: imx: scu: Do not enable runtime PM for CPU clks

Since CPU clocks are managed by CPUFREQ and ATF, do not enable
runtime PM otherwise rpm gets out of status as cpufreq
also manages clock states.

Signed-off-by: Nitin Garg <nitin.garg@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>