imx: Generalize disable_cpu_nodes

disable_cpu_nodes could be reused by i.MX9, so move disable_cpu_nodes
out from mach-imx/imx8m/soc.c to mach-imx/fdt.c and update
disable_cpu_nodes to make it easy to support different socs.

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