Staging: comedi: COMEDI_BUFINFO with no async - report no bytes read or written

When the COMEDI_BUFINFO ioctl is used on a subdevice without
asynchronous streaming command support, set 'bytes_read = 0' and
'bytes_written = 0' in the buffer info returned back to the user.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/comedi_fops.c

@@ -584,6 +584,8 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 		bi.buf_read_ptr = 0;
 		bi.buf_write_count = 0;
 		bi.buf_read_count = 0;
+		bi.bytes_read = 0;
+		bi.bytes_written = 0;
 		goto copyback;
 	}