staging: comedi: adv_pci_dio: remove CheckAndAllocCard()

This driver creates a linked list of all the pci devices in
the system while it's looking for a match. It's only use is
to determine if a device is "free" to use. The pci_is_enabled()
helper can give us the same information. Use that instead and
remove the linked list.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>