hso: fix memory leak in hso_create_rfkill()

When the rfkill interface was created, a buffer containing the name
of the rfkill node was allocated. This buffer was never freed when the
device disappears.

To fix the problem, we put the name given to rfkill_alloc() in
the hso_net structure.

Signed-off-by: Olivier Sobrie <olivier@sobrie.be>
Signed-off-by: David S. Miller <davem@davemloft.net>