leds: is31fl32xx: Use struct_size() helper

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 is31fl32xx_priv {
	...
        struct is31fl32xx_led_data leds[0];
};

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes.

So, replace the following function:

static inline size_t sizeof_is31fl32xx_priv(int num_leds)
{
       return sizeof(struct is31fl32xx_priv) +
                     (sizeof(struct is31fl32xx_led_data) * num_leds);
}

with:

struct_size(priv, leds, count)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Signed-off-by: Jacek Anaszewski <[email protected]>

drivers/leds/leds-is31fl32xx.c

@@ -324,12 +324,6 @@ static int is31fl32xx_init_regs(struct is31fl32xx_priv *priv)
 	return 0;
 }
 
-static inline size_t sizeof_is31fl32xx_priv(int num_leds)
-{
-	return sizeof(struct is31fl32xx_priv) +
-		      (sizeof(struct is31fl32xx_led_data) * num_leds);
-}
-
 static int is31fl32xx_parse_child_dt(const struct device *dev,
 				     const struct device_node *child,
 				     struct is31fl32xx_led_data *led_data)
@@ -450,7 +444,7 @@ static int is31fl32xx_probe(struct i2c_client *client,
 	if (!count)
 		return -EINVAL;
 
-	priv = devm_kzalloc(dev, sizeof_is31fl32xx_priv(count),
+	priv = devm_kzalloc(dev, struct_size(priv, leds, count),
 			    GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;