cxgb4: cxgb4_tc_u32: use struct_size() in kvzalloc()

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

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

instance = kvzalloc(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: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_u32.c

@@ -444,8 +444,7 @@ struct cxgb4_tc_u32_table *cxgb4_init_tc_u32(struct adapter *adap)
 	if (!max_tids)
 		return NULL;
 
-	t = kvzalloc(sizeof(*t) +
-			 (max_tids * sizeof(struct cxgb4_link)), GFP_KERNEL);
+	t = kvzalloc(struct_size(t, table, max_tids), GFP_KERNEL);
 	if (!t)
 		return NULL;