NFC: Fix LLCP sockets releasing path

The socket local pointer needs to be set to NULL when the adapter is
removed or the MAC goes down.
If the socket release code is called after such an event, the socket
reference count still needs to be decreased in order for the socket to
eventually be freed.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>