staging: comedi: cb_das16_cs: cleanup das16cs_ai_rinsn()

Cleanup to analog input read function.

1) Initialize the chan, range, and aref locale variables when
   they are declared.
2) Remove need for the static local variable.
3) Remove the unnecessary cast of inw()'s return value.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/cb_das16_cs.c

@@ -111,16 +111,11 @@ static int das16cs_ai_rinsn(struct comedi_device *dev,
 			    struct comedi_insn *insn, unsigned int *data)
 {
 	struct das16cs_private *devpriv = dev->private;
+	int chan = CR_CHAN(insn->chanspec);
+	int range = CR_RANGE(insn->chanspec);
+	int aref = CR_AREF(insn->chanspec);
 	int i;
 	int to;
-	int aref;
-	int range;
-	int chan;
-	static int range_bits[] = { 0x800, 0x000, 0x100, 0x200 };
-
-	chan = CR_CHAN(insn->chanspec);
-	aref = CR_AREF(insn->chanspec);
-	range = CR_RANGE(insn->chanspec);
 
 	outw(chan, dev->iobase + 2);
 
@@ -129,7 +124,22 @@ static int das16cs_ai_rinsn(struct comedi_device *dev,
 	outw(devpriv->status1, dev->iobase + 4);
 
 	devpriv->status2 &= ~0xff00;
-	devpriv->status2 |= range_bits[range];
+	switch (range) {
+	case 0:
+		devpriv->status2 |= 0x800;
+		break;
+	case 1:
+		devpriv->status2 |= 0x000;
+		break;
+	case 2:
+		devpriv->status2 |= 0x100;
+		break;
+	case 3:
+		devpriv->status2 |= 0x200;
+		break;
+	default:
+		return -EINVAL;
+	}
 	outw(devpriv->status2, dev->iobase + 6);
 
 	for (i = 0; i < insn->n; i++) {
@@ -144,7 +154,7 @@ static int das16cs_ai_rinsn(struct comedi_device *dev,
 			dev_dbg(dev->class_dev, "cb_das16_cs: ai timeout\n");
 			return -ETIME;
 		}
-		data[i] = (unsigned short)inw(dev->iobase + 0);
+		data[i] = inw(dev->iobase + 0);
 	}
 
 	return i;