regulator: da9063: 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;
    struct boo entry[];
};

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

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

instance = alloc(struct_size(instance, entry, count), GFP_KERNEL)

Notice that, in this case, variable size is not necessary, hence it is
removed.

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>

drivers/regulator/da9063-regulator.c

@@ -739,7 +739,6 @@ static int da9063_regulator_probe(struct platform_device *pdev)
 	struct regulator_config config;
 	bool bcores_merged, bmem_bio_merged;
 	int id, irq, n, n_regulators, ret, val;
-	size_t size;
 
 	regl_pdata = da9063_pdata ? da9063_pdata->regulators_pdata : NULL;
 
@@ -784,9 +783,8 @@ static int da9063_regulator_probe(struct platform_device *pdev)
 		n_regulators--;    /* remove BMEM_BIO_MERGED */
 
 	/* Allocate memory required by usable regulators */
-	size = sizeof(struct da9063_regulators) +
-		n_regulators * sizeof(struct da9063_regulator);
-	regulators = devm_kzalloc(&pdev->dev, size, GFP_KERNEL);
+	regulators = devm_kzalloc(&pdev->dev, struct_size(regulators,
+				  regulator, n_regulators), GFP_KERNEL);
 	if (!regulators)
 		return -ENOMEM;