phy: samsung: Use struct_size() in devm_kzalloc()

One of the more common cases of allocation size calculations is finding the size of a structure that has a zero-sized array at the end, along with memory for some number of elements for that array. For example:

struct samsung_usb2_phy_driver {
	...
        struct samsung_usb2_phy_instance instances[0];
};

instance = devm_kzalloc(dev, sizeof(struct samsung_usb2_phy_driver) + count *

			sizeof(struct samsung_usb2_phy_instance), GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now use the new struct_size() helper:

instance = devm_kzalloc(dev, struct_size(instance, instances, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

---
 drivers/phy/samsung/phy-samsung-usb2.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

index ea818866985a..4616ec829900 100644
@@ -159,9 +159,8 @@ static int samsung_usb2_phy_probe(struct platform_device *pdev)
 	if (!cfg)
 		return -EINVAL;
 
-	drv = devm_kzalloc(dev, sizeof(struct samsung_usb2_phy_driver) +
-		cfg->num_phys * sizeof(struct samsung_usb2_phy_instance),
-								GFP_KERNEL);
+	drv = devm_kzalloc(dev, struct_size(drv, instances, cfg->num_phys),
+			   GFP_KERNEL);
 	if (!drv)
 		return -ENOMEM;
 

2.21.0