staging: comedi: ni_labpc_common: fix logically dead code issue

The quick exit check of (mode == MODE_SINGLE_CHAN) results in coverity
reporting a logically dead code issue in the switch code in
labpc_ai_check_chanlist().

Remove the quick exit check and allow the function to handle the
MODE_SINGLE_CHAN normally (the for loop will only happen 1 time and
the function will return 0).

Reported-by: coverity (CID 1222108)
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>

drivers/staging/comedi/drivers/ni_labpc_common.c

@@ -482,9 +482,6 @@ static int labpc_ai_check_chanlist(struct comedi_device *dev,
 	unsigned int aref0 = CR_AREF(cmd->chanlist[0]);
 	int i;
 
-	if (mode == MODE_SINGLE_CHAN)
-		return 0;
-
 	for (i = 0; i < cmd->chanlist_len; i++) {
 		unsigned int chan = CR_CHAN(cmd->chanlist[i]);
 		unsigned int range = CR_RANGE(cmd->chanlist[i]);