[PATCH -next] xen-pciback: Fix return in pm_ctrl_init()

[YueHaibing]

Return NULL instead of passing to ERR_PTR while err is zero,
this fix smatch warnings:
drivers/xen/xen-pciback/conf_space_capability.c:163
 pm_ctrl_init() warn: passing zero to 'ERR_PTR'

Fixes: a92336a1176b ("xen/pciback: Drop two backends, squash and cleanup some code.")
Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
---
 drivers/xen/xen-pciback/conf_space_capability.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/xen-pciback/conf_space_capability.c b/drivers/xen/xen-pciback/conf_space_capability.c
index 22f13abbe913..5e53b4817f16 100644
--- a/drivers/xen/xen-pciback/conf_space_capability.c
+++ b/drivers/xen/xen-pciback/conf_space_capability.c
@@ -160,7 +160,7 @@ static void *pm_ctrl_init(struct pci_dev *dev, int offset)
 	}
 
 out:
-	return ERR_PTR(err);
+	return err ? ERR_PTR(err) : NULL;
 }
 
 static const struct config_field caplist_pm[] = {
-- 
2.17.1