staging: comedi: das6402: use comedi_request_region()

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

Remove the default iobase address (0x300) that is used when the user
does not pass a base address during the "comedi_config". Comedi
legacy drivers should only attach to a specified address.

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

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>