hso: fix rfkill name conflicts

By using only the usb interface number for the rfkill name, we might
have a name conflicts in case two similar hso devices are connected.

In this patch, the name of the hso rfkill interface embed the value
of a counter that is incremented each time a new rfkill interface is
added.

Suggested-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: Olivier Sobrie <olivier@sobrie.be>
Signed-off-by: David S. Miller <davem@davemloft.net>