The problem was that the semaphore which prevents ds interfering with
the sleepy card initialisation (skt_sem in pccardd) is blocking insmod
of the socket driver.  However, the socket driver is being called with
the PCI bus semaphore held by the driver model.

pccardd in turn discovered a cardbus card (with skt_sem held), so it
is trying to add the PCI devices to the PCI bus, and this requires the
driver model to grab the PCI bus semaphore, but its already locked.

We move the class device register into pccardd so we get a natural
ordering between the ds socket initialisation and pccardd trying to
detect inserted cards.

We also fix a potential use-after-free caused by rmmod'ing the socket
driver before ds has shut down.