sc16is7xx: 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 foo {
    int stuff;
    void *entry[];
};

instance = devm_kzalloc(dev, sizeof(struct foo) + sizeof(void *) * count, 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, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

---
 drivers/tty/serial/sc16is7xx.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

index 268098681856..635178cf3eed 100644
@@ -1187,9 +1187,7 @@ static int sc16is7xx_probe(struct device *dev,
 		return PTR_ERR(regmap);
 
 	/* Alloc port structure */
-	s = devm_kzalloc(dev, sizeof(*s) +
-			 sizeof(struct sc16is7xx_one) * devtype->nr_uart,
-			 GFP_KERNEL);
+	s = devm_kzalloc(dev, struct_size(s, p, devtype->nr_uart), GFP_KERNEL);
 	if (!s) {
 		dev_err(dev, "Error allocating port structure\n");
 		return -ENOMEM;

2.20.1