staging: comedi: remove pci_is_enabled() tests

As mentioned by Ian Abbott, the comedi pci drivers that try to
locate an unused pci device with the pci_is_enabled() test
might actually skip over a perfectly good unused device. This
test is also not consistent with the other comedi pci drivers.

Remove the test from all the comedi pci drivers.

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