Switch pcmcia_bus_socket's reference counting to struct kref.  Also, split the
access by number into two calls, so that get_bus_socket can be used in a more
generic way.
Signed-off-by: Dominik Brodowski <linux@brodo.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>