power: domain: add i.MX8 scu power domain driver

power: domain: add i.MX8 scu power domain driver

The power domain tree is not accepted by Linux Kernel upstream.
only a single pd node is used currently, as following:

		pd: imx8qx-pd {
			compatible = "fsl,imx8qm-scu-pd", "fsl,scu-pd";
			#power-domain-cells = <1>;
		};

So to migrate to use upstream linux dts, we also need a driver
to support this.

This patch is to support the new method, compared with legacy power
domain tree, it will be simpiler, because each device will
has resource id as power domain index, it will be directly passed
to scfw, and no need to let power domain build that tree. If multiple
power domain is needed, it is the dts node should has correctly power
domains entry added and sequence correct.

Signed-off-by: Peng Fan <peng.fan@nxp.com>