device property: Make fwnode_handle_get() return the fwnode

The fwnode_handle_get() function is used to obtain a reference to an
fwnode. A common usage pattern for the OF equivalent of the function is:

	mynode = of_node_get(node);

Similarly make fwnode_handle_get() return the fwnode to which the
reference was obtained.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>