misc: enclosure: Use struct_size() in 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 = kzalloc(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 = kzalloc(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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/enclosure.c

@@ -125,9 +125,7 @@ enclosure_register(struct device *dev, const char *name, int components,
 		   struct enclosure_component_callbacks *cb)
 {
 	struct enclosure_device *edev =
-		kzalloc(sizeof(struct enclosure_device) +
-			sizeof(struct enclosure_component)*components,
-			GFP_KERNEL);
+		kzalloc(struct_size(edev, component, components), GFP_KERNEL);
 	int err, i;
 
 	BUG_ON(!cb);