serial: max310x: 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.

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 drivers/tty/serial/max310x.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

drivers/tty/serial/max310x.c +1 -2

index 4f479841769a..1d700a8ab517 100644
@@ -1197,8 +1197,7 @@ static int max310x_probe(struct device 
 *dev, struct max310x_devtype *devtype,
 		return PTR_ERR(regmap);
 
 	/* Alloc port structure */
-	s = devm_kzalloc(dev, sizeof(*s) +
-			 sizeof(struct max310x_one) * devtype->nr, GFP_KERNEL);
+	s = devm_kzalloc(dev, struct_size(s, p, devtype->nr), GFP_KERNEL);
 	if (!s) {
 		dev_err(dev, "Error allocating port structure\n");

return -ENOMEM;