ice: Use struct_size() helper

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:

size = struct_size(instance, entry, count);

This code was detected with the help of Coccinelle.
Signed-off-by: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ice/ice_sched.c

@@ -683,10 +683,10 @@ ice_sched_add_elems(struct ice_port_info *pi, struct ice_sched_node *tc_node,
 	u16 i, num_groups_added = 0;
 	enum ice_status status = 0;
 	struct ice_hw *hw = pi->hw;
-	u16 buf_size;
+	size_t buf_size;
 	u32 teid;
 
-	buf_size = sizeof(*buf) + sizeof(*buf->generic) * (num_nodes - 1);
+	buf_size = struct_size(buf, generic, num_nodes - 1);
 	buf = devm_kzalloc(ice_hw_to_dev(hw), buf_size, GFP_KERNEL);
 	if (!buf)
 		return ICE_ERR_NO_MEMORY;