drivers/regulator: use PTR_ERR to get error code

IS_ERR returns only 1 or 0.  The callsite of setup_regulators expects a
negative integer in an error case.  Thus, PTR_ERR has to be used to extract
it.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression E,E1;
@@

*E = IS_ERR(...)
 ... when != E = E1
*return E;
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Acked-by: <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

drivers/regulator/lp3971.c

@@ -446,8 +446,8 @@ static int setup_regulators(struct lp3971 *lp3971,
 		lp3971->rdev[i] = regulator_register(&regulators[id],
 			lp3971->dev, pdata->regulators[i].initdata, lp3971);
 
-		err = IS_ERR(lp3971->rdev[i]);
-		if (err) {
+		if (IS_ERR(lp3971->rdev[i])) {
+			err = PTR_ERR(lp3971->rdev[i]);
 			dev_err(lp3971->dev, "regulator init failed: %d\n",
 				err);
 			goto error;