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>
diff --git a/net/nfc/hci/hcp.c b/net/nfc/hci/hcp.c
index bc308a7..b6b4109 100644
--- a/net/nfc/hci/hcp.c
+++ b/net/nfc/hci/hcp.c
@@ -105,6 +105,13 @@
 	}
 
 	mutex_lock(&hdev->msg_tx_mutex);
+
+	if (hdev->shutting_down) {
+		err = -ESHUTDOWN;
+		mutex_unlock(&hdev->msg_tx_mutex);
+		goto out_skb_err;
+	}
+
 	list_add_tail(&cmd->msg_l, &hdev->msg_tx_queue);
 	mutex_unlock(&hdev->msg_tx_mutex);