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.
Also, address the following sparse warnings:
drivers/usb/host/xhci-mtk-sch.c:265:20: warning: using sizeof on a flexible structure
Link: https://github.com/KSPP/linux/issues/160
Link: https://github.com/KSPP/linux/issues/174
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Acked-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>