MLK-17074-10 soc: imx8: pm-domains: fix missing full intialization for root domain...

MLK-17074-10 soc: imx8: pm-domains: fix missing full intialization for root domain nodes

Current power domain driver only setup all domain callbacks during second
level power domains intialization. However, there're also some root power
domain nodes having valid SC resource handler which may be used by device
as well. Missing to setup them may result in some features lost on these
domains.
e.g.
pd_dc0: PD_DC_0 {
	compatible = "nxp,imx8-pd";
	reg = <SC_R_DC_0>;
	#power-domain-cells = <0>;
	#address-cells = <1>;
	#size-cells = <0>;
	...
}

Reviewed-by: Frank Li <frank.li@nxp.com>
Reviewed-by: Ranjani Vaidyanathan <Ranjani.Vaidyanathan@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>