CVE-2026-46047: net: qrtr: ns: Fix use-after-free in driver remove()

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

net: qrtr: ns: Fix use-after-free in driver remove()

In the remove callback, if a packet arrives after destroyworkqueue() is called, but before sockrelease(), the qrtrnsdataready() callback will try to queue the work, causing use-after-free issue.

Fix this issue by saving the default 'skdataready' callback during qrtrnsinit() and use it to replace the qrtrnsdataready() callback at the start of remove(). This ensures that even if a packet arrives after destroyworkqueue(), the work struct will not be dereferenced.

Note that it is also required to ensure that the RX threads are completed before destroying the workqueue, because the threads could be using the qrtrnsdataready() callback.