CVE-2026-68461: device property: initialize the remaining fields of fwnode_handle in fwnode_init()

In the Linux kernel, the following vulnerability has been resolved: device property: initialize the remaining fields of fwnode_handle in fwnode_init() If a firmware node is allocated on the stack (for instance: temporary software node whose life-time we control) or on the heap - but using a non-zeroing allocation function - and initialized using fwnode_init(), its secondary pointer will contain uninitialized memory which likely will be neither NULL nor IS_ERR() and so may end up being dereferenced (for example: in dev_to_swnode()). Set fwnode->secondary to NULL on initialization. While at it: initialize the remaining fields of struct fwnode_handle too just to be sure. [ Fix typo in commit message. - Danilo ]