staging: comedi: amplc_pc236: cleanup "find pci device" code

staging: comedi: amplc_pc236: cleanup "find pci device" code

For aesthetic reasons, rename the function and pass the
comedi_devconfig struct instead of pre-parsing out the bus/slot
information.

Use for_each_pci_dev() instead of open-coding the loop using
pci_get_device().

Consolidate the dev_err messages when a pci device is not found.

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>