staging: comedi: ni_65xx: use comedi_buf_write_samples()

Use comedi_buf_write_samples() to add the sample to the async buffer.

The async events COMEDI_CB_EOS will automatically be set by the core
with the end-of-scan is detected. Remove the unnecessary event in the
driver.

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