staging: comedi: rtd520: ioremap'ed addresses are resource_size_t

As mentioned by Ian Abbott, the pci address passed to ioremap
should be a resource_size_t not an unsigned long. Use a local
variable of that type to hold the pci_resource_start() that is
passed to ioremp().

Set the dev->iobase to a dummy non-zero value so that the "detach"
can use it as a flag to know that comedi_pci_disable() needs to
be called.

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>