software node: Simplify software_node_release() function

It's possible to release the node ID immediately when
fwnode_remove_software_node() is called, no need to wait for
software_node_release() with that.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>