NFC: Fixed nfc core and hci unregistration and cleanup

When an adapter is removed, it will unregister itself from hci and/or
nfc core. In order to do that safely, work tasks must first be canceled
and prevented to be scheduled again, before the hci or nfc device can be
destroyed.

Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/net/nfc/hci.h

@@ -87,6 +87,8 @@ struct nfc_hci_dev {
 
 	u32 max_data_link_payload;
 
+	bool shutting_down;
+
 	struct mutex msg_tx_mutex;
 
 	struct list_head msg_tx_queue;

include/net/nfc/nfc.h

@@ -115,6 +115,8 @@ struct nfc_dev {
 	struct timer_list check_pres_timer;
 	struct work_struct check_pres_work;
 
+	bool shutting_down;
+
 	struct nfc_ops *ops;
 };
 #define to_nfc_dev(_dev) container_of(_dev, struct nfc_dev, dev)