staging: comedi: me_daq: factor out the PLX bug workaround

Factor out the code in me_attach_pci() that handles the PLX-Bug
workaround to a separate function.

This looks odd. It appears that the bug workaround either swaps
PCI bars 0 and 5 or it modifies PCI bar 0. Shouldn't this happen
before PCI bar 0 is ioremap'ed?

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>