net: nfc: nci: Change the NCI close sequence

If there is a NCI command in work queue after closing the NCI device at
nci_unregister_device, The NCI command timer starts at flush_workqueue
function and then NCI command timeout handler would be called 5 second
after flushing the NCI command work queue and destroying the queue.
At that time, the timeout handler would try to use NCI command work queue
that is destroyed already. it will causes the problem. To avoid this
abnormal situation, change the sequence to prevent the NCI command timeout
handler from being called after destroying the NCI command work queue.

Signed-off-by: Bongsu Jeon <bongsu.jeon@samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>