ASoC: dapm: Use struct_size() in krealloc()

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;
    struct boo entry[];
};

instance = krealloc(instance, sizeof(struct foo) + count * sizeof(struct boo), GFP_KERNEL);

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

instance = krealloc(instance, struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-dapm.c

@@ -487,7 +487,8 @@ static int dapm_kcontrol_add_widget(struct snd_kcontrol *kcontrol,
 		n = 1;
 
 	new_wlist = krealloc(data->wlist,
-			sizeof(*new_wlist) + sizeof(widget) * n, GFP_KERNEL);
+			     struct_size(new_wlist, widgets, n),
+			     GFP_KERNEL);
 	if (!new_wlist)
 		return -ENOMEM;