staging: comedi: ni_at_ao: use comedi_request_region()

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

Remove the board attach noise as well as the error 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>