staging: comedi: rtd520: remove 'got_regions' from private data

staging: comedi: rtd520: remove 'got_regions' from private data

The 'got_regions' variable in the private data is used as a flag
for the detach to know if the pci device has been enabled.

Typically the dev->iobase variable is used to indicate this in
all the other comedi drivers. Do the same here for consistancy.

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>