mlxsw: spectrum_nve: 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;
    struct boo entry[];
};

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

This issue was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c

@@ -267,8 +267,8 @@ mlxsw_sp_nve_mc_record_create(struct mlxsw_sp *mlxsw_sp,
 	struct mlxsw_sp_nve_mc_record *mc_record;
 	int err;
 
-	mc_record = kzalloc(sizeof(*mc_record) + num_max_entries *
-			    sizeof(struct mlxsw_sp_nve_mc_entry), GFP_KERNEL);
+	mc_record = kzalloc(struct_size(mc_record, entries, num_max_entries),
+			    GFP_KERNEL);
 	if (!mc_record)
 		return ERR_PTR(-ENOMEM);