staging: comedi: fix comedi_nsamples_left.

A rounding error was causing comedi_nsamples_left to
return the wrong value when nsamples was not a multiple
of the scan length.

Cc: <[e-mail]> # v4.4+
Signed-off-by: Frank Mori Hess <[e-mail]>
Reviewed-by: Ian Abbott <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/comedi/drivers.c

···
 	struct comedi_cmd *cmd = &async->cmd;
 
 	if (cmd->stop_src == TRIG_COUNT) {
-		unsigned int nscans = nsamples / cmd->scan_end_arg;
-		unsigned int scans_left = __comedi_nscans_left(s, nscans);
+		unsigned int scans_left = __comedi_nscans_left(s, cmd->stop_arg);
 		unsigned int scan_pos =
 		    comedi_bytes_to_samples(s, async->scan_progress);
 		unsigned long long samples_left = 0;