wdfserial: fix NULL pipe guards and divide-by-zero in read/write threads#21

5656hcx merged 3 commits intoqualcomm:mainqualcomm/qcom-usb-kernel-drivers:mainfrom

hangzqcom:fix/null-pipe-guard-reset-usb-pipehangzqcom/qcom-usb-kernel-drivers:fix/null-pipe-guard-reset-usb-pipeCopy head branch name to clipboard