dt: add of_platform_populate() for creating device from the device tree

dt: add of_platform_populate() for creating device from the device tree

of_platform_populate() is similar to of_platform_bus_probe() except
that it strictly enforces that all device nodes must have a compatible
property, and it can be used to register devices (not buses) which are
children of the root node.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>