regulator: da9062: 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>
Acked-by: Steve Twiss <stwiss.opensource@diasemi.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/da9062-regulator.c

@@ -992,7 +992,6 @@ static int da9062_regulator_probe(struct platform_device *pdev)
 	struct regulator_config config = { };
 	const struct da9062_regulator_info *rinfo;
 	int irq, n, ret;
-	size_t size;
 	int max_regulators;
 
 	switch (chip->chip_type) {
@@ -1010,9 +1009,8 @@ static int da9062_regulator_probe(struct platform_device *pdev)
 	}
 
 	/* Allocate memory required by usable regulators */
-	size = sizeof(struct da9062_regulators) +
-		max_regulators * sizeof(struct da9062_regulator);
-	regulators = devm_kzalloc(&pdev->dev, size, GFP_KERNEL);
+	regulators = devm_kzalloc(&pdev->dev, struct_size(regulators, regulator,
+				  max_regulators), GFP_KERNEL);
 	if (!regulators)
 		return -ENOMEM;