OPP: Fix passing 0 to PTR_ERR in _opp_attach_genpd()

If dev_pm_domain_attach_by_name() returns NULL, then 0 will be passed to
PTR_ERR() as reported by the smatch warning below:

drivers/opp/core.c:2456 _opp_attach_genpd() warn: passing zero to 'PTR_ERR'

Fix it by checking for the non-NULL virt_dev pointer before passing it to
PTR_ERR. Otherwise return -ENODEV.

Fixes: 4ea9496 ("opp: Fix error check in dev_pm_opp_attach_genpd()")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Author: Mani-Sadhasivam

drivers/opp/core.c

@@ -2460,7 +2460,7 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
 
 		virt_dev = dev_pm_domain_attach_by_name(dev, *name);
 		if (IS_ERR_OR_NULL(virt_dev)) {
-			ret = PTR_ERR(virt_dev) ? : -ENODEV;
+			ret = virt_dev ? PTR_ERR(virt_dev) : -ENODEV;
 			dev_err(dev, "Couldn't attach to pm_domain: %d\n", ret);
 			goto err;
 		}