staging: comedi: das1800: use __comedi_request_region()

staging: comedi: das1800: use __comedi_request_region()

Use __comedi_request_region() to request the additional I/O region
used by this driver.

Remove the error message when the request_region() fails,
comedi_request_reqion() will output the error message if necessary.

For aesthetic reasons, rename the local variable 'retval' to
simply 'ret'.

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>