staging: comedi: addi_apci_2032: use comedi_buf_write_samples()

The dev->read_subdev used in this driver for async commands returns the
full scan with each sample so it should have the SDF_PACKED subdev_flag
set.

Add the missing subdev_flags and use comedi_buf_write_samples() to add
the sample to the async buffer.

The core sets the async events appropriately. Remove the unnecessary
event handling 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>