extcon: usbc-cros-ec: Use struct_size() helper in kzalloc()

Make use of the struct_size() helper instead of an open-coded version,
in order to avoid any potential type mistakes or integer overflows that,
in the worst scenario, could lead to heap overflows.
Signed-off-by: NGustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: NChanwoo Choi <cw00.choi@samsung.com>

drivers/extcon/extcon-usbc-cros-ec.c

@@ -68,7 +68,7 @@ static int cros_ec_pd_command(struct cros_ec_extcon_info *info,
 	struct cros_ec_command *msg;
 	int ret;
 
-	msg = kzalloc(sizeof(*msg) + max(outsize, insize), GFP_KERNEL);
+	msg = kzalloc(struct_size(msg, data, max(outsize, insize)), GFP_KERNEL);
 	if (!msg)
 		return -ENOMEM;