net: appletalk: Fix device refcount leak in atrtr_create()

In the Linux kernel, the following vulnerability has been resolved: net: appletalk: Fix device refcount leak in atrtr_create() When updating an existing route entry in atrtr_create(), the old device reference was not being released before assigning the new device, leading to a device refcount leak. Fix this by calling dev_put() to release the old device reference before holding the new one.