device property: fix of node refcount leak in fwnode_graph_get_next_endpoint()

In the Linux kernel, the following vulnerability has been resolved:

device property: fix of node refcount leak in fwnode_graph_get_next_endpoint()

The 'parent' returned by fwnode_graph_get_port_parent()

with refcount incremented when 'prev' is not NULL, it

needs be put when finish using it.

Because the parent is const, introduce a new variable to

store the returned fwnode, then put it before returning

from fwnode_graph_get_next_endpoint().