memory: fsl_ifc: populate child devices without relying on simple-bus

After we update the binding to not use simple-bus compatible for the
controller, we need the driver to populate the child devices explicitly.

Signed-off-by: Li Yang <leoyang.li@nxp.com>
Link: https://lore.kernel.org/r/20211116211846.16335-3-leoyang.li@nxp.com
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>