usb: roles: fix of node refcount leak in usb_role_switch_is_parent()

I got the following report while doing device(mt6370-tcpc) load
test with CONFIG_OF_UNITTEST and CONFIG_OF_DYNAMIC enabled:

  OF: ERROR: memory leak, expected refcount 1 instead of 2,
  of_node_get()/of_node_put() unbalanced - destroy cset entry:
  attach overlay node /i2c/pmic@34

The 'parent' returned by fwnode_get_parent() with refcount incremented.
it needs be put after using.

Fixes: 6fadd729

 ("usb: roles: get usb-role-switch from parent")
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221122111226.251588-1-yangyingliang@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>