staging: comedi: cb_das16_cs: remove unneeded default case in analog in read

The default (return -EINVAL) case is not needed when working
out the correct value to set the analog input range. As pointed
out by Ian Abbott, the comedi core checks the range in
comedi_check_chanlist() before calling the insn_read() function.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Reported-by: NIan Abbott <abbotti@mev.co.uk>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/cb_das16_cs.c

@@ -136,8 +136,6 @@ static int das16cs_ai_rinsn(struct comedi_device *dev,
 	case 3:
 		devpriv->status2 |= 0x200;
 		break;
-	default:
-		return -EINVAL;
 	}
 	outw(devpriv->status2, dev->iobase + DAS16CS_MISC2);